Internal frames, sometimes called floating frames, appear as separate boxes or windows within a Web page rather than on one side. An internal frame can be placed within a page in the same way that in-line images are placed within pages. To create an internal frame, you use the <IFRAME> tag, which is similar to the <IMG> tag. Like <IMG>, the <IFRAME> tag supports the attributes SRC, WIDTH, HEIGHT, ALIGN, HSPACE, and VSPACE. Furthermore, like the <FRAME> tag, it supports the attributes FRAMEBORDER, MARGINHEIGHT, and MARGINWIDTH for controlling the appearance of the internal frame borders, and the SCROLLING attribute for turning scrollbars on or off. You can also use the NAME attribute if you need to direct hyperlink targets to the internal frame.
Unlike the <IMG> tag, however, an <IFRAME> tag must have a closing </IFRAME> tag. The text that appears within the tag will be displayed only if the user's browser is incapable of displaying internal frames. Another limitation is that Netscape Navigator is currently unable to display internal frames, even though this feature is included in the HTML 4.01 standard.