Web Design in a Nutshell, 3rd Edition

id identifier

The id attribute is used to give an element a specific and unique name in the document. In the earlier div example, id was used to label a section of the page as “sidebar.” That means there may be no other element with id="sidebar" in that document (although, it is okay if it appears in other documents on the same site). ID values must be unique.

The HTML 4.01 Recommendation specifies the following uses for id attribute:

• As a style sheet selector

• As a target anchor for links (with the same functionality as <a name="">)

• As a means to access an element from a script

• As the name of a declared object element

• For general purpose processing by user agents, essentially treating the element as data