Compatibility view is a feature first introduced with Microsoft Internet Explorer 8.0 that enables the browser to enter a mode that allows it to support pages that may not have all the latest browser features. Enabling this view will set features back to Internet Explorer 7 and will fix issues such as misaligned text, images, or text boxes, issues with scripts, and some crash situations.
Above is a picture and an example of how to enable this mode. As can be seen, clicking the broken green page will switch between compatibility view and non-compatibility view.
If you are a webmaster who would like to remove this from your web page or want to have your pages emulate IE7, you could do either of the below solutions.
Add the below meta tag to each of your pages. This tag must be placed before any other meta tags for it to work.
<meta http-equiv="X-UA-Compatible" content="IE=EmulateIE7">
If you would like to make this change throughout your site and do not want to edit every page edit your .htaccess file and add the below lines into that file.
# Emulate IE7 to prevent compatibility view
BrowserMatch "^.*MSIE 8.*$" emulate_ie7
Header set X-UA-Compatible "IE=EmulateIE7" env=emulate_ie7
Also see: Internet Explorer