There’s been several blog postings here about how to set your web pages so they will display in Internet Explorer 8 out-of-the-box as they would have in Internet Explorer 7. The challenge is that Internet Explorer 8 renders pages in a more standards-compliant manner by default. And that change can affect how pages that were tweaked for Internet Explorer 7 work.
Hanu Kommalapati has written a blog entry that explains the steps to set backwards compatibility in the Apache 2.2 HTTP Server configuration. The response can be set at the server level, directory level or within the individual HTML page. His blog entry Apache httpd configuration for IE7 standard mode rendering in IE8 provides the details.