With the release of Windows Internet Explorer 8, the latest Standards mode will be the default rendering mode. Content written for previous versions of Internet Explorer might display differently than intended.
Issues you might experience when you use Windows Internet Explorer 8 Beta include:
1) Misaligned Web page layouts.
2) Overlapping text or images.
The Compatibility View mode in Internet Explorer 8 Beta 2 helps ensure that your web site can be viewed without display or functionality issues. Compatibility View represents a big improvement over “Emulate IE7” mode in Beta 1 because compatibility can now be set on a site by site basis rather than for the whole browser session and has been enhanced to be compatible with more sites.
For more information on the Compatibility View mode we invite you to watch this brief video overview.
To further resolve compatibility issues, web site owners and administrators can add a meta-tag that tells Windows Internet Explorer 8 to display an entire site or a specific page like Windows Internet Explorer 7. For instructions on adding the meta tag, either on a per-site or per-page basis, visit the Windows Internet Explorer Compatibility Center.
More Info- http://msdn.microsoft.com/en-us/ie/cc405106.aspx