function getQueryVariable(variable)
{
       var query = window.location.search.substring(1);
       var vars = query.split("&");
       for (var i=0;i<vars.length;i++) {
               var pair = vars[i].split("=");
               if(pair[0] == variable){return pair[1];}
       }
       return(false);
}

http://css-tricks.com/snippets/javascript/get-url-variables/

Example URL:
http://www.example.com/index.php?id=1&image=awesome.jpg

getQueryVariable(”id”) – would return “1″.
Calling getQueryVariable(”image”) – would return “awesome.jpg”.

Get URL Variables

JavaScript