HTML techniques and developments

Style Sheets
Over the years, HTML has been extended to include elements that deal with the design of the document, which ran contrary to the original idea of the system independence. A return to the separation of content (structure) and layout was done by the definition of Cascading Style Sheets (CSS).

Thus, the appearance of the document is in a separate file, which defines the so-called stylesheet. This improves the adaptability of the layout to the respective output device, and to specific user needs, such as the visually impaired. Today, the support for CSS, means the browser has a sophisticated design.

Dynamic HTML
Very early in the history of HTML, additional techniques were invented, making it possible to dynamically modify HTML documents while viewing in the browser. The most common is JavaScript. These techniques were developed by different browser vendors, notably Microsoft and Netscape, independently of one another.

Therefore, there were significant problems in the implementation of techniques between different browsers. Meanwhile, all widely interpreted JavaScript-enabled browsers used the Document Object Model (DOM). This makes it possible to write scripts executable on all browsers. However, there are still differences in the support of the DOM standard.

XML
Meanwhile, the latest version of the HTML standard was (HTML 4.01) in the metalanguage XML. The resulting XHTML 1.0 was compared to SGML syntactic rules of XML. Currently, the XHTML standard in version 1.1 is available, which introduces an additional modularization of the elements.

The future universal format XML itself is increasingly being used. This also works with tags that can be used very restrictively by document type definition (DTD). XML thus enables a self describing data model. For the conversion of data stored in XML data into the appropriate display formats.

Ajax
Ajax describes the combination of known techniques such as JavaScript, XML and DOM. The goal here is dynamic pages that can respond like desktop applications.
Different interpretation of web documents

Despite the provisions in the standards, there is still available different browsers on different representations of the same website. One of the main reasons is the different handling of errors in the output.

But even valid (accurate) sites can be represented differently, as not all standards are met by all browsers equally. There are differences both in HTML and the CSS and JavaScript.

Even in the same browser the same document is presented differently depending on the used document type. Therefore, it is useful during the development of a site to test each equal representation, or to at least ensure that all major site contents can be reached despite differences in presentation.