frames - Are they cool?

I have read so many conflicting reports on whether it is acceptable to use iFrames or not.

What is the general consensus?

Thanks

The only problem is related with the search engines. SE is instructed to search the representative words in the document's text and compare them with the querry and with the meta tags and the title of the document.

SE might consider the content of an iframe/frame more reprentative than the parent, so that it will rise the iframed page in its result classification. Now the user will open the iframe alone and will loose the parent (which usually bear the menu) - A famous case is http://www.quirksmode.org

You may use a javascript code to force the iframe loading only inside the parent, but some SE woun't like that, and might consider the entire site as a fake, and it will lower it in their classification.