The term web server can mean one of two things:
1. A computer program that is responsible for accepting HTTP requests from clients, which are known as web browsers, and serving them HTTP responses along with optional data contents, which usually are web pages such as HTML documents and linked objects (images, etc.).
2. A computer that runs a computer program which provides the functionality described in the first sense of the term.
Some of the most popular software, which Servers run to allow them to respond to client request for information, is Internet Information Server (IIS), Apache Web Server, Netscape Server, and Microsoft Personal Web Server.
Although web server programs differ in detail, they all share some basic common features.
1. HTTP: every web server program operates by accepting HTTP requests from the client, and providing an HTTP response to the client. The HTTP response usually consists of an HTML document, but can also be a raw file, an image, or some other type of document (defined by MIME-types); if some error is found in client request or while trying to serve the request, a web server has to send an error response which may include some custom HTML or text messages to better explain the problem to end users.
2. Logging: usually web servers have also the capability of logging some detailed information, about client requests and server responses, to log files; this allows the webmaster to collect statistics by running log analyzers on log files.
In practice many web servers implement the following features also:
1. Authentication, optional authorization request (request of user name and password) before allowing access to some or all kind of resources.
2. Handling of not only static content (file content recorded in server's filesystem(s)) but of dynamic content too by supporting one or more related interfaces (SSI, CGI, SCGI, FastCGI, JSP, PHP, ASP, ASP .NET, Server API such as NSAPI, ISAPI, etc.).
3. HTTPS support (by SSL or TLS) to allow secure (encrypted) connections to the server on the standard port 443 instead of usual port 80.
4. Content compression (i.e. by gzip encoding) to reduce the size of the responses (to lower bandwidth usage, etc.).
5. Virtual hosting to serve many web sites using one IP address.
6. Large file support to be able to serve files whose size is greater than 2 GB on 32 bit OS.
Bandwidth throttling to limit the speed of responses in order to not saturate the network and to be able to serve more clients.
HTTP Request Types
Request Methods
HTTP defines eight methods (sometimes referred to as "verbs") indicating the desired action to be performed on the identified resource.
HEAD
Asks for the response identical to the one that would correspond to a GET request, but without the response body. This is useful for retrieving meta-information written in response headers, without having to transport the entire content.
GET
Requests a representation of the specified resource. By far the most common method used on the Web today. Should not be used for operations that cause side-effects (using it for actions in web applications is a common misuse). See 'safe methods' below.
POST
Submits data to be processed (e.g. from an HTML form) to the identified resource. The data is included in the body of the request. This may result in the creation of a new resource or the updates of existing resources or both.
PUT
Uploads a representation of the specified resource.
DELETE
Deletes the specified resource.
TRACE
Echoes back the received request, so that a client can see what intermediate servers are adding or changing in the request.
OPTIONS
Returns the HTTP methods that the server supports. This can be used to check the functionality of a web server.
CONNECT
Converts the request connection to a transparent TCP/IP tunnel, usually to facilitate SSL-encrypted communication (HTTPS) through an unencrypted HTTP proxy.
Introduction to Microsoft IIS
Microsoft Internet Information Services (IIS, formerly called Internet Information Server) is a set of Internet-based services for servers using Microsoft Windows. It is the world's second most popular web server in terms of overall websites, behind Apache HTTP Server. As of October 2007 it served 37.13% of all websites and 38.23% of all active websites according to Netcraft. The servers currently include FTP, SMTP, NNTP, and HTTP/HTTPS.
Internet Information Services 7.0
Debuting with Windows Vista, and also to be included in Windows Server 2008, IIS 7.0 features a modular architecture. Instead of a monolithic server which features all services, IIS 7 has a core web server engine. Modules offering specific functionality can be added to the engine to enable its features. The advantage of having this architecture is that only the features required can be enabled and that the functionalities can be extended by using custom modules.
IIS 7 will ship with a handful of modules, but Microsoft will make other modules available online.[8] The following sets of modules are slated to ship with the server:
HTTP Modules
Security Modules
Content Modules
Compression Modules
Caching Modules
Logging and Diagnostics Modules
Writing extensions to IIS 7 using ISAPI has been deprecated in favor of the module API, which allows modules can plug in anywhere in the request processing pipeline. Much of IIS's own functionality is built on this API, and as such, developers will have much more control over a request process than was possible in prior versions. Modules can be written using C++, or using the IHttpModule interface from a .NET Framework language. Modules can be loaded globally where the services provided by the module can effect all sites, or loaded on a per-site basis. IIS 7 has an integrated mode application pool where .NET modules are loaded into the pipeline using the module API, rather than ISAPI. As a result ASP.NET code can be used with all requests to the server.[9] For applications requiring strict IIS 6.0 compatibility, the Classic application pool mode loads asp.NET as an ISAPI.
A significant change from previous versions of IIS is that all web server configuration information is stored solely in XML configuration files, instead of in the metabase. The server has a global configuration file that provides defaults, and each virtual web's document root (and any subdirectory thereof) may contain a web.config containing settings that augment or override the defaults. Changes to these files take effect immediately. This marks a significant departure from previous versions whereby web interfaces, or machine administrator access, were required to change simple settings such as default document, active modules and security/authentication. It also eliminates the need to perform metabase synchronization between multiple servers in a farm of web servers.
IIS 7 also features a completely rewritten administration interface that takes advantage of modern MMC features such as task panes and asynchronous operation. Configuration of ASP.NET is more fully integrated into the administrative interface.
Creating Virtual Directories in IIS 6.0 (IIS 6.0)
In most cases, the content you publish to your Web or FTP site is located in a root or home directory on your computer, such as C:\Inetpub\Wwwroot\. However, there might be instances when the content is located somewhere else, or even on a remote computer.
To publish from any directory not contained within your home or root directory, you can create a virtual directory. A virtual directory is a directory that is not contained in the home directory but appears to client browsers as though it were.
You can create a virtual directory through IIS Manager or by using Windows Explorer. Additionally, you can create a Web virtual directory by using the Iisvdir.vbs script, and a FTP virtual directory by using the Iisftpdr.vbs script.
Important
You must be a member of the Administrators group on the local computer to perform the following procedure or procedures. As a security best practice, log on to your computer by using an account that is not in the Administrators group, and then use the runas command to run IIS Manager as an administrator. At a command prompt, type runas /user:Administrative_AccountName "mmc %systemroot%\system32\inetsrv\iis.msc".
Procedures
To create a virtual directory by using IIS Manager
1. In IIS Manager, expand the local computer, expand the Web Sites or FTP Sites folder, right-click the site or folder within which you want to create the virtual directory, point to New, and then click Virtual Directory. The Virtual Directory Creation Wizard appears.
2. Click Next.
3. In the Alias box, type a name for the virtual directory. (Choose a short name that is easy to type because the user types this name.)
4. Click Next.
5.In the Path box, type or browse to the physical directory in which the virtual directory resides, and then click Next.
6. Under Allow the following permissions, select the check boxes for the access permissions you want to assign to your users, and then click Next.
Important
For security reasons, when selecting access permissions, consider allowing only the default Read permission. By restricting permissions in this way, you can help avoid attacks against your Web site by malicious users. For more information about setting access permissions, see Securing Virtual Directories and Access Control in Help and Support Center for Windows Server 2003.
7. Click Finish. The virtual directory is created below the currently selected folder level.
To create a virtual directory by using Windows Explorer
1. Open Windows Explorer.
2. Right-click the folder you want to be a virtual directory, and click Sharing and Security.
3. Click the Web Sharing tab.
4. Click Share this folder.
5. In the Alias box, type the name for the virtual directory.
6. Click OK twice.
To create a Web virtual directory by using the Iisvdir.vbs script
1. From the Start menu, click Run.
2. In the Open box, type cmd, and then click OK.
3. At the command prompt, type the following:
cscript %SystemRoot%\system32\iisvdir.vbs /create SampleWebSite[/Path] VirtualDirectorydrive:\path
where SampleWebSite, VirtualDirectory, and path is the physical directory, as appropriate.
To create an FTP virtual directory by using the Iisftpdr.vbs script
1. From the Start menu, click Run.
2. In the Open box, type cmd, and then click OK.
3. At the command prompt, type the following:
cscript %SystemRoot%\system32\iisftpdr.vbs /create FTPSite[/Path] VirtualDirectory drive:\path
where FTPSite, VirtualDirectory, and path is the physical directory, as appropriate.
DHTML
Dynamic HTML or DHTML is a collection of technologies used together to create interactive and animated web sites by using a combination of a static markup language (such as HTML), a client-side scripting language (such as JavaScript), a presentation definition language (Cascading Style Sheets, CSS), and the Document Object Model.
A DHTML webpage is any webpage in which client-side scripting changes variables of the presentation definition language, which in turn affects the look and function of otherwise "static" HTML page content, after the page has been fully loaded and during the viewing process. Thus the dynamic characteristic of DHTML is the way it functions while a page is viewed, not in its ability to generate a unique page with each page load.
By contrast, a dynamic web page is a broader concept — any web page generated differently for each user, load occurrence, or specific variable values. This includes pages created by client side scripting, and ones created by server-side scripting (such as PHP or Perl) where the web server generates content before sending it to the client.
CSS
In web development, Cascading Style Sheets (CSS) is a stylesheet language used to describe the presentation of a document written in a markup language. Its most common application is to style web pages written in HTML and XHTML, but the language can be applied to any kind of XML document, including SVG and XUL.
CSS is used to help readers of web pages to define colors, fonts, layout, and other aspects of document presentation. It is designed primarily to enable the separation of document content (written in HTML or a similar markup language) from document presentation (written in CSS). This separation can improve content accessibility, provide more flexibility and control in the specification of presentation characteristics, and reduce complexity and repetition in the structural content. CSS can also allow the same markup page to be presented in different styles for different rendering methods, such as on-screen, in print, by voice (when read out by a speech-based browser or screen reader) and on Braille-based, tactile devices. CSS specifies a priority scheme to determine which style rules apply if more than one rule matches against a particular element. In this so-called cascade, priorities or weights are calculated and assigned to rules, so that the results are predictable.
Syntax
CSS has a simple syntax, and uses a number of English keywords to specify the names of various style properties.
A style sheet consists of a list of rules. Each rule or rule-set consists of one or more selectors and a declaration block. A declaration-block consists of a list of semicolon-terminated declarations in curly braces. Each declaration itself consists of a property, a colon (:), a value, then a semi-colon (;).
In CSS, selectors are used to declare which elements a style applies to, a kind of match expression. Selectors may apply to all elements of a specific type, or only those elements which match a certain attribute; elements may be matched depending on how they are placed relative to each other in the markup code, or on how they are nested within the document object model.
In addition to these, a set of pseudo-classes can be used to define further behavior. Probably the best-known of these is :hover, which applies a style only when the user 'points to' the visible element, usually by holding the mouse cursor over it. It is appended to a selector as in a:hover or #elementid:hover. Other pseudo-classes and pseudo-elements are, for example, :first-line, :visited or :before. A special pseudo-class is :lang(c), "c".
A pseudo-class selects entire elements, such as :link or :visited, whereas a pseudo-element makes a selection that may consist of partial elements, such as :first-line or :first-letter.
Selectors may be combined in other ways too, especially in CSS 2.1, to achieve greater specificity and flexibility.
Use of CSS
Prior to CSS, nearly all of the presentational attributes of HTML documents were contained within the HTML markup; all font colors, background styles, element alignments, borders and sizes had to be explicitly described, often repeatedly, within the HTML. CSS allows authors to move much of that information to a separate stylesheet resulting in considerably simpler HTML markup.
Headings (h1 elements), sub-headings (h2), sub-sub-headings (h3), etc., are defined structurally using HTML. In print and on the screen, choice of font, size, color and emphasis for these elements is presentational.
Prior to CSS, document authors who wanted to assign such typographic characteristics to, say, all h2 headings had to use the HTML font and other presentational elements for each occurrence of that heading type. The additional presentational markup in the HTML made documents more complex, and generally more difficult to maintain. To render all h2 tags in this manner, the markup had to be repeated for each heading. In CSS, presentation is separated from structure. In print, CSS can define color, font, text alignment, size, borders, spacing, layout and many other typographic characteristics. It can do so independently for on-screen and printed views. CSS also defines non-visual styles such as the speed and emphasis with which text is read out by aural text readers. The W3C now considers the advantages of CSS for defining all aspects of the presentation of HTML pages to be superior to other methods. It has therefore deprecated the use of all the original presentational HTML markup.
ASP
Active Server Pages (ASP) is Microsoft's first server-side script engine for dynamically-generated web pages. It was initially marketed as an add-on to Internet Information Services (IIS) via the Windows NT 4.0 Option Pack, but has been included as a free component of Windows Server since the initial release of Windows 2000 Server. Programming ASP websites is made easier by various built-in objects. Each object corresponds to a group of frequently-used functionality useful for creating dynamic web pages. In ASP 2.0 there are six such built-in objects: Application, ASPError, Request, Response, Server, and Session. Session, for example, is a cookie-based session object that maintains variables from page to page. Websites using ASP can be identified as they use .asp instead of .htm or .html as a filename extension.
Most ASP pages are written in VBScript, but any other Active Scripting engine can be selected instead by using the Language directive or the script language="language" runat="server"> syntax. JScript (Microsoft's implementation of ECMAScript) is the other language that is usually available. PerlScript (a derivative of Perl) and others are available as third-party installable Active Scripting engines
Microsoft Visual InterDev
Microsoft Visual InterDev, part of Microsoft Visual Studio 97 and 6.0, is an IDE used to create web applications using Microsoft Active Server Pages (ASP) technologies. It has code completion, database server management tools, and an integrated debugger.
Visual InterDev provides a robust, integrated development environment to address the many capabilities of the Web. You can integrate various technologies, like ActiveX controls and Active Server Components, to create a powerful application. The integrated development environment enables you to use scripting languages like VBScript and JavaScript to create dynamic applications and Web pages. You can work on simultaneous projects of different types all from within Visual InterDev's Developer Studio interface. In addition to Visual InterDev projects, you also can develop Visual C++ and Visual J++ projects.
