Windows Internet Explorer 8 (IE8) is the latest web browser developed by Microsoft in the long running Internet Explorer browser series. The browser was released on March 19, 2009 for Windows XP, Windows Server 2003, Windows Vista and Windows Server 2008. Both 32-bit and 64-bit builds are available. It is the successor to Internet Explorer 7, released in 2006, and is the default browser for the upcoming Windows 7 and Windows Server 2008 R2 operating systems.

Source: Wikipedia

Rally is working on compliance with native IE8 but probably won't be completely compliant until later this year.

Until then, you may notice Rally display improperly using IE8.  Most IE8 problems are related to the new rendering engine, where its behavior differs significantly from that of IE7. IE8 Standards Mode is the default rendering engine to use on running the browser, thus may break compatibility of some websites - including Rally.

As such, it may be a good practice to configure IE8 so that all websites are loaded in IE7 Standards Mode. IE8 provides an easy way to let user decides if an individual website (or a domain) should be displayed in compatibility view, with a tiny “broken paper” icon at the end of the address bar. In order to minimize any risk of browser crashes, it’s best to force all websites and web pages to display in IE8 Compatibility View browser mode, which loads the pages in IE7 Standards document mode.

In order to enable and turn on Compatibility View mode for all web pages and websites, click on Tools menu, and select Compatibility View Settings. In the “Compatibility View Settings” dialog, click the check box for Display all websites in Compatibility View option. Click on Close button when done.

The IE7 Standards document mode in IE8 Compatibility View mode is activated immediately, which makes IE8 behaves a little bit more like IE7.