xWindow is somewhat old - but still works well. Here's another demo illustrating its use.
Also see the first demo.
Forum support is available at the X Library Support Forums.
The X core is designed to work with all browsers, Object-detection instead of browser-detection is used exclusively. Currently, I'm testing with the following browsers. X has been tested by others on a wide variety of platforms.
Win7 (Home): IE 9.
WinXP (SP3): Chrome 220.127.116.11, Firefox 3.5.5, IE 7 & 8, Opera 10.60 and Safari 4.0.3.
Linux (Ubuntu 9.10): Chrome 18.104.22.168 and FireFox 3.5.7.