In the words of Adobe, "BrowserLab provides web designers exact renderings of their web pages in multiple browsers and operating systems, on demand." Most of the time when I'd like to do a quick browser compatibility test I already have the site in consideration open in Safari and/or Firefox and would like to check IE support, so I thought a browser-based bookmarklet would be a good thing to add to my development toolkit. So I did what any good developer would do — I wrote one. (Of course, this doesn't replace the necessity for in-depth browser testing before site delivery and/or deployment, but it does provide a good starting point for basic testing.)
To install the bookmarklet: just drag this link into your browser's bookmarks toolbar (here's an example, using Safari):
To use the bookmarklet, just click on it when you're on a site or page that you'd like to test, and the current site will be opened in Adobe BrowserLab, ready to load using variety of different browsers for compatibility testing. (Note: you'll need an Adobe account, and it'll ask you for your password each time you use the application — there's no "remember me" feature.)