When creating a Website, the content and structure of that site is defined within the XHTML code. "Content" specifically refers to all text, images, files, etc. that will be on a website. The designer can determine what each part of the content is by utilizing "XHTML markup", or tags, which are defined using angle brackets ( <> ) . For example, if the designer wanted certain text to be a title, they could tag that text using the h1 tag. However, if they wanted the text below the title to be smaller and lighter, the designer could define that text as a paragraph using the p tag. Images can also be defined by tags, specifically the img tag.
While the overall content and structure of a webpage is found in XHTML, how that content is styled and presented is determined in CSS, or Cascading Style Sheets. Utilizing CSS, a website designer can change and edit different attributes of the elements found in XHTML code. For example, the size, weight, and positioning of a line of text can all be determined in CSS code. An example of how text size would be coded in CSS is as follows:
p {font-size: 12px;}
A good website is one that can be accessed and viewed easily on a variety of different devices. In order for this to be achieved, a designer must make sure that their XHTML is valid and well-formed, and that their CSS is also valid. Well-formed refers to XHTML that is structured in accordance with the markup rules. These rules are as follows: Declare a DOCTYPE; declare an XML namespace; declare your content type; close every tag, whether enclosing or nonenclosing; all tags must be nested correctly; inline tags can't contain block level tags; write tags entirely in lowercase; attributes must have values and must be coded; and use the encoded equivalents for a left angle bracket and ampersand within content.