Description

In a frameset, the individual windows (or frames) can only be laid in rows or columns, although in days gone by developers found cunning (read: overcomplicated) ways of creating pages where content could appear to be in the middle of a page, apparently floating. Doing this required a complex mess of nested framesets, as if the page were some kind of jigsaw. The iframe was the answer to this problem, providing a window that could be placed anywhere within an existing, non frame-based page, much as you could place a table or an image.

The iframe has a number of attributes that are unique to this element (in the context of it being a window/frame), namely it can be given a fixed height and width and also be set to align with surrounding content, much as an image can; it also shares some attributes with the frame element, namely the longdesc, marginheight, marginwidth, name, scrolling and src attributes.

The iframe differs from the frame in one other way that is worth noting:

• the frame element is self closing, and thus does not contain anything (there is no closing </frame> tag). To present content to browser that do not understand/support frames, you use the noframes element inside the parent frameset element
• with the iframe, there is both an opening <iframe> and closing </iframe> tag, and there is no requirement for noframes - to present content for browsers that do not understand the iframe, you simply place it between these opening and closing tags, as demonstrated in the example HTML

Note that iframe is not available to use when specifying strict HTML and XHTML doctypes.