Glad I'm ahead of you (note the folders in the top image!) I've been using Link bar folders since at least the Netscape 4.0, and likely the Netscape 3.x days. Yes, it also works in the various Internet Explorer versions, going at least back to version 4.x.

I agree with you. It definitely saves me time. Did you notice the Firefox link within the folder that allows you to open all the bookmarks within that folder into separate tabs? I use that at work to open all the tabs I regularly use with just two clicks (one to open the folder, the second to open six tabs).