If we are talking B2C web sites (i.e. where you cannot guarantee the user's technical set up) then my view is, don't use frames. I appreciate that is a little black and white but I have yet to find any compelling reasons why frames should be used and plenty why they should not.

Reasons to use frames:
1. 'Ease of navigation' - some people claim they like to have the main navigation always present and that frames are therefore necessary. I have yet to read any anecdotal or hard data that supports this. A 'back to top' link seems to do the trick.

Reasons not to use frames:
1. The browser compatibility argument is increasingly less valid these days as frames are supported by Navigator 2 and Internet Explorer 3 and up, which themselves are old browsers by any standards.

2. Bookmarking pages is more difficult with frames as the URL is not page specific. Workarounds are possible but more complicated.

3. Site speed. The site can be slightly slower as more requests for separate HTML pages are being sent to the server to make up a single screen view.

4. Search engines. Many search engines’ robots cannot spider and index frames-based sites. It is harder to submit specific pages with targeted keywords and body text (called ‘portal’ or ‘doorway’ pages e.g. for a specific product) if the page belongs in a frameset.

5. Links. Again, because of the URL, it is trickier (though still possible) to give external sites a direct link to a particular page within your site if it needs to be part of a frameset containing multiple other pages.

6. Printing. Browsers will print the frame that has focus by default. This could lead to confusion with some users.

7. Statistical reporting. The more frames there are, the harder it is to accurately track usage across a site and give accreditable page impression figures.

8. Banner ads. If you plan to have banner ads on your site, you should think twice before having a frame-laden site. Advertising space is most often sold by CPM – cost per thousand page impressions. A page impression is registered by the ad server software every time a new banner is loaded. If you have no frames it is easy, as every link to a new page will refresh the banner ad. If you have a few frames it is trickier but still quite possible to refresh the banner ad page when the user goes to each new section. With many frames, however, the frame targeting and page refreshing becomes much more complex and messy, possibly resulting in cross-browser and scripting issues and lost revenue due to the banner ad not always properly refreshing.

9. Programming. The more frames there are the harder it becomes to keep track of all the HTML files and make cross site changes. File and site management in general becomes less easy.

10. Content management systems. Large, information driven sites that use content management systems to dynamically publish content to the web do not work well with designs that use many frames.

11. Padlock and Key. If you use frames then be aware that in order for the browser padlock to close or key to become whole, showing users that they are on a secure page, all the pages within the frameset need to be secure. If you only have the page which takes the credit card details secure but others in the frameset are not, the padlock will remain open giving users the impression their credit card details are not going to securely transmitted.

Am I being unfairly biased against frames? Think of the top sites in the world - how many of them use frames? You've got to wonder why not...

Looking at the A List Apart article again, I see it only addresses the (very important) URL issue. And it actually doesn't mention the very clever solution on the MSDN site to this problem, which is "get URL for this page" -- and ASP script that reloads the page with a unique frameset for the current content.

Solving the URL problem addresses most of the important problems you mentioned, although at the loss of some of the benefits of frames, as the article points out.

Here are solutions to other important problems:
1. Printing: "Print this page" links where content is likely to be printed -- which are necessary for non-framed sites too, to avoid printing unnecessary navigation.
2. A CMS may in fact aid in easily providing the above (although I'm speaking in theory, as I've not implemented one myself). A CMS may also aid in lessening the work in providing <noframes> content for an entire site, which addresses both the accessibility and robots issue.

francois