When designing and producing web documents, the designer should ensure that their semantics and structure are well reflected by the markup and code they contain.
Semantic tags help with orientation in the document and are also useful in automatic processing. If we do not use tags for their original purposes, or we use headings randomly, regardless of the document's structure, all semantic information carried by the document will be lost and all benefits of structure will be denied.
The essential message conveyed by the document may be preceded only by information required to be known before the user starts reading the message.
Details: The code adheres to this order of information: prologue - statement - other information.
The only reason for visiting our site is the information we provide. Any other pieces of information must therefore be located after the main statement, for users are at first interested in main statement and then they care about the rest. If this main information is not to be found easily, the user leaves without further studying your pages' content.
Details: The prologue must contain document identification with first level heading, which may be used only once in the whole document and should introduces document's statement. Furthermore it contains only information needed for understanding document's meaning and context of content. Everything that doesn't belong to prologue, nor to the main statement, should be placed after this main information.
Prior to the main information only the necessary facts may appear - anything else must be, if possible, placed below it. Those necessary facts are document's identification, which introduces its content, or placing it into the context of surrounding documents. Top-level heading usually does that. Traditionally the heading is considered the name of the document, it must therefore be used only once in the document.
Some other information which ease understanding and using document may be placed in the prologue. For example links into the document's content, links for alternative language versions, links for other document's layouts (i.e. alternative style sheets) etc. Everything the reader needn't know before reading content, must not appear in the prologue.
Using style sheets may attain another layout. Even here the aim is to render the main statement to dominate the page.
The body of a web document must not contain markup the value of which is not intended to convey structural or semantic information; nor should the body contain any content the sole purpose of which is to enrich the visual presentation of the document.
Non-semantic tags must not be used in the document. Author must assume any of possible ways of document's presentation. Visual presentations are made with i.e. cascading styles or scripts. "Neutral" tags <div> and <span> may be used, since they do not have semantical, nor presentational meaning.
Details: Document's body must not contain objects or pictures, whose only purpose is presentation, or those with informational value equal to depicting text.
Pictures without informational value, which exist only as a part of graphical layout, must not be present in the document. They may be displayed using i.e. cascading styles. Pictures may contain text only if it expresses its graphical presentation (preview of typography, logotype etc.). So displayed text must not be part of the document's convey.