Get visitor screen resolution using javascript

This script helps you to find screen resolution of a client / user machine and redirect to a webpage. In the code below I am checking 3 different screen resolutions like 640×480 , 800×600 and 1024×768

<script LANGUAGE="JavaScript">
function resolution_finder() {
var url640x480 = "http://www.yahoo.com";
var url800x600 = "http://www.googl.com";
var url1024x768 = "http://www.msn.com";
if ((screen.width == 640) && (screen.height == 480)) 
window.location.href= url640x480;
else if ((screen.width == 800) && (screen.height == 600))
window.location.href= url800x600;
else if ((screen.width == 1024) && (screen.height == 768))
window.location.href= url1024x768;
else window.location.href= url640x480;
}
</script>

The HTML source

<center>
<form>
<input type=button value="Click Me And Redirect" onClick="resolution_finder()"/>
</form>
</center>

Incoming search terms:

• else if screen width (1)
• script for find screen width height (1)