HTML is a true extension of SGML. HTML does a few things differently:
- HTML restricts which SGML tags are allowed to be used on a web page
- HTML creates a dedicated tag (<a>) known as the anchor tag to reference other documents
HTML’s ability to cross-reference documents helped it gain rapid popularity amongst researchers and scientists. Research documents can easily link to or reference other documents to create a web of information. In 1990, Tim Berners-Lee published a formal proposal titled WorldWideWeb that described a system of hypertext documents viewed by software named browsers in a client-server architecture. World Wide Web Consortium
Not long after the first two HTML proposals (HTML 1.0 and HTML 2.0 respectively), Tim Berners-Lee founded and led the World Wide Web Consortium (W3C). The group of member organizations and staff worked together to develop new standards for the World Wide Web on a regular basis. The W3C has created specifications for HTML, XML, CSS and even XHTML.
Cascading Style Sheets (CSS) is a language that controls and allows one to define the look of an HTML document. It permits the separation between the content of the HTML document from the style of the HTML file. CSS enables one to specify things such as the font you want on your page, the size of your text, the columns of the page, whether the text on a page is to be in bold or italics, background, link colors, margins, and placement of objects on a page and so on. by way of explanation, it is the part that controls the looks of a web page. With CSS, it is much easier to manage the appearance of multiple web pages since it separates the HTML element from display information. CSS also enables faster downloading of web pages, which is works best with older computers and modems. It provides a method for retaining a common style.
The coding of CSS style rules can be done in three places, namely:
Inline – done in the HTML tag.
Internal Style Sheet – coded at the beginning of a HTML document i.e. inside the tags, and closed by the tags.
External Style Sheet – this is a separate file with a .css extension which serves as a reference for multiple HTML pages with a path/link in the HTML pages pointing to browsers where to look for the styles.
Add multimedia elements such as showing, hiding, changing, creating image role overs, scrolling text across the status bar, etc.
Form processing such as user input validation during the form submission, modify the contents of the form.