You can force IE to use compatibility mode with X-UA-Compatible Meta Tag:
IE 7:
<meta http-equiv="X-UA-Compatible" value="IE=7">
IE 8:
<meta http-equiv="X-UA-Compatible" value="IE=8">
IE 9:
<meta http-equiv="X-UA-Compatible" value="IE=9">
IE look also at the page DOCTYPE:
Standards View
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<title>This page is NOT Rendered in Compatibility View</title>
</head>
<body>
<h1>This page is NOT Compatibility View</h1>
</body>
</html>
Compatibility View
<html>
<head>
<title>This page is NOT Rendered in Compatibility View</title>
</head>
<body>
<h1>This page is NOT Compatibility View</h1>
</body>
</html>
Standards View
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html>
<head>
<title>This page is NOT Rendered in Compatibility View</title>
</head>
<body>
<h1>This page is NOT Compatibility View</h1>
</body>
</html>
Compatibility View
<?xml version="1.0" encoding="UTF-8">
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html>
<head>
<title>This page is NOT Rendered in Compatibility View</title>
</head>
<body>
<h1>This page is NOT Compatibility View</h1>
</body>
</html>
Note, that last example should load as standards view in XHTML mode. But Internet Explorer interprets that XML declaration as requiring compatibility view.