function insertParam(key, value)
{    key = escape(key); value = escape(value);
    var kvp = document.location.search.substr(1).split('&');
    var i=kvp.length; var x; while(i--)
     {        x = kvp[i].split('=');
        if (x[0]==key)        { 
               x[1] = value;                kvp[i] = x.join('=');                break;
        }    }
    if(i<0) {kvp[kvp.length] = [key,value].join('=');}
   document.location.search = kvp.join('&'); }