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What is the difference between HTML and XHTML?

admin — Sat, 14 Feb 2009 11:27:23 +0000

The differences between HTML and XHTML are small. As the rules of XHTML are based on those of XML, the same exceptionally strict rules apply as with XML. The major differences are outlined below.

The most important difference between the two markup languages is that HyperText Markup Language, or HTML, is an application of SGML (Standard Generalized Markup Language)1 and allows an author to omit certain tags and use attribute minimization. The Extensible HyperText Markup Language, or XHTML, is an application of XML (Extensible Markup Language). It doesnâ€™t permit the omission of any tags or the use of attribute minimization. XHTML documents must start with an XHTML DocType declaration.

The following chart shows what the differences between HTML and XHTML are:

HTML 4.01	XHTML 1.0
Forgiving	Requires discipline and attention to detail
Correct nesting required in theory	Correct nesting absolutely required
Some end tags optional	All end tags required
No end tag for empty content model	Even empty content model requires end tag
Case insensitive	Lowercase only
Some attribute values needn’t be quoted	All attribute values must be quoted
Certain “valueless” attribute values are OK	All attributes must have values
Less sensitive to special characters	More sensitive to special characters
Ubiquitous name attribute	Id attribute preferred to name, mostly

What is SSI?

admin — Sat, 14 Feb 2009 11:06:21 +0000

SSI stands for “server-side include,” a type of HTML instruction telling a computer that serves Web pages to dynamically generate data, usually by inserting certain variable contents into a fixed template or boilerplate Web page. Used especially in database searches. In order to use Server Side Includes, your server must be configured to support them.

SSI can help make your pages more responsive and can even help make maintaining your site an easier task. SSI is primarily used to “paste” the contents of one or more files into another. For example, a file (of any type, .html, .txt, etc.) containing a daily quote could be included into multiple SSI-enabled pages throughout a website by placing the following code into the desired pages:

There is no official standard for SSIs, so every Web server is free to support different SSIs in different manners. However, many SSI commands, such as #include and #exec, have become de facto standards.

Server Side Includes
Pros:
Change one file and every file that uses that include is instantly updated.
Every server language supports them in one form or another.
Easier to reuse code pieces.

Cons:
Server has to parse each page that uses includes, which can slow down your server and make your site feel slower.

What is a URL?

admin — Sat, 14 Feb 2009 10:54:59 +0000

URL is an acronym for Uniform Resource Locator and is a reference (an address) to a resource on the Internet. The unique address of any Web document. The following is an example of a URL which addresses the Java Web site hosted by Sun Microsystems:

As in the previous diagram, a URL has two main components:

Protocol identifier
Resource name

Note that the protocol identifier and the resource name are separated by a colon and two forward slashes. The protocol identifier indicates the name of the protocol to be used to fetch the resource. The example uses the Hypertext Transfer Protocol (HTTP), which is typically used to serve up hypertext documents. HTTP is just one of many different protocols used to access different types of resources on the net. Other protocols include File Transfer Protocol (FTP), Gopher, File, and News.

The resource name is the complete address to the resource. The format of the resource name depends entirely on the protocol used, but for many protocols, including HTTP, the resource name contains one or more of the components listed in the following table:

Host Name	The name of the machine on which the resource lives.
Filename	The pathname to the file on the machine.
Port Number	The port number to which to connect (typically optional).
Reference	A reference to a named anchor within a resource that usually identifies a specific location within a file (typically optional).

Source: java.sun.com

What is XHTML?

admin — Sat, 14 Feb 2009 10:47:21 +0000

The Extensible Hypertext Markup Language, or XHTML, is a hybrid between HTML and XML that is more universally acceptable in Web pages and search engines than XML. Both standards are powerful, but XHTML is significantly better than HTML.

XHTML uses three XML namespaces (used to qualify element and attributes names by associating them with namespaces identified by URI references. Namespaces prevent identically custom-named tags that may be used in different XML documents from being read the same way), which correspond to three HTML 4.0 DTDs: Strict, Transitional, and Frameset.

A character encoding may be specified at the beginning of an XHTML document in the XML declaration when the document is served using the application/xhtml+xml MIME type. (If an XML document lacks encoding specification, an XML parser assumes that the encoding is UTF-8 or UTF-16, unless the encoding has already been determined by a higher protocol.)

For example:

< ?xml version="1.0" encoding="UTF-8"?>

What is WIKI?

admin — Sat, 14 Feb 2009 10:41:13 +0000

Wiki is a piece of server software that allows users to freely create and edit Web page content using any Web browser. Wiki supports hyperlinks and has a simple text syntax for creating new pages and crosslinks between internal pages on the fly.

Wiki is a term meaning “quick” in Hawaiian, that is used for technology that gathers in one place a number of web pages focused on a theme, project, or collaboration. Wikis are generally used when users or group members are invited to develop, contribute, and update the content of the wiki.

A wiki invites all users to edit any page or to create new pages within the wiki Web site, using only a plain-vanilla Web browser without any extra add-ons. Wiki promotes meaningful topic associations between different pages by making page link creation almost intuitively easy and showing whether an intended target page exists or not.

Wikis can be passworded in various ways to control or allow contributions. The most famous wiki is the Wikipedia.