Some of our clients have expressed an interest in learning more about these various technologies, so we present this brief guide for your edification.
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- XHTML - Extensible Hypertext Markup Language
The abbreviation HTML, for Hypertext Markup Language, is practically ubiquitous. It was the original markup language that made the World Wide Web possible because it was simple enough for non-programmers to write web pages with it. It has undergone several revisions and extensions, the last of which was in December 1999. The website of the World Wide Web Consortium (W3C) has the specification archived, but it is a highly technical document, written more for web browser manufacturers than anyone else.
It is highly unlikely that HTML will be revised further, yet the World Wide Web continues to grow in scope and ability exponentially. The W3C wisely decided that HTML simply wouldn't be able to cope with what the Web would throw at it in the future. They chose to reformulate HTML as an application of XML (Extensible Markup Language). XML's extensible nature makes it "forward-compatible" with future technologies, and so a version of HTML made with XML would have access to those new technologies too. The new specification was called XHTML (Extensible Hypertext Markup Language).
XHTML is virtually identical to HTML. This makes it compatible with HTML, and consequently it is compatible with earlier web browsers that support HTML. Element tags must be in lowercase and closed, and attribute values must always be properly quoted. Besides those, there really isn't that much difference between the two. Because of this, Keystone Websites chooses to use XHTML in all website construction to guarantee that pages we create will be accessible for many years to come.
- CSS - Cascading Style Sheets
Style sheets have been around in one form or another since the beginnings of HTML in the early 1990s. Various browsers included their own style language which could be used to customize the appearance of web documents. Originally, style sheets were targeted towards the end-user; early revisions of HTML did not provide many facilities for presentational attributes, so it was often up to the user to decide how web documents would appear.
The concept of Cascading Style Sheets was originally proposed in 1994 by Håkon Wium Lie. Bert Bos was at the time working on a browser called Argo which used its own style sheets and the two decided to work together to develop CSS. A number of other style sheet languages had already been proposed, but CSS was the first to incorporate the idea of "cascading" -- the capability for a document's style to be inherited from more than one "style sheet." This permitted a user's preferred style to override the site author's specified style in some areas, while inheriting, or "cascading" the author's style in other areas. The capability to cascade in this way permits both users and site authors added flexibility and control; it permitted a mixture of stylistic preferences.
Håkon's proposal was presented at the "Mosaic and the Web" conference in Chicago in 1994, and again with Bert Bos in 1995. Around this time, the World Wide Web Consortium was being established; the W3C took an interest in the development of CSS, and organized a workshop toward that end. Håkon and Bert were the primary technical staff on the project, with additional members, including Thomas Reardon of Microsoft, participating as well. By the end of 1996, CSS was nearly ready to become official. The CSS level 1 Recommendation was published in December 1996.
Early in 1997, CSS was assigned its own working group within the W3C, chaired by Chris Lilley. The group began tackling issues that had not been addressed with CSS level 1, resulting in the creation of CSS level 2, which was published as an official Recommendation in May 1998. CSS level 3 is still under development as of 2003.
CSS is now used for styling XHTML (which lacks presentational markup in some circumstances) and XML, as well as other related technologies. Because it allows a web designer to completely separate the content of a web document from its presentation, it is a technology that we at Keystone Websites have embraced eagerly. An entire site can be altered visually by simply changing a few rules in a style sheet - the kind of thing that was previously only possible with templating.
- PHP - PHP Hypertext Preprocessor
PHP is one of the most popular server-side scripting systems on the Web. It's been widely adopted since the release of version 4, which was the first version powered by the powerful Zend Engine from Zend Technologies. Originally designed by Rasmus Lerdorf, in 1994, to display his resume information and collect some data, such as how many hits it was generating, it has been developed into a very powerful language. Like Microsoft's Active Server Pages (ASP), PHP is very easy to learn, but unlike ASP it can run on pretty much any platform.
When combined with the Linux platform, the Apache web server, and the MySQL database (and forming the new acronym of "LAMP"), developers can take advantage of a highly configurable suite of tools with very little cost. All these technologies are designed to work together - and it shows, with high performance and sophisticated control. PHP has become the server-side scripting language of choice for Keystone Websites, mainly because it can be deployed in any environment. In fact, PHP is used extensively "under the hood" of this website.