function AjaxQuitPrealable() {

    var xhr;
    try {xhr = new ActiveXObject('Msxml2.XMLHTTP'); }
    catch (e) 
    {
        try {xhr = new ActiveXObject('Microsoft.XMLHTTP'); }
        catch (e2) 
        { try { xhr = new XMLHttpRequest();  }
          catch (e3) {  xhr = false;   }
        }
    }
   

xhr.open("GET","QuitPrealable.aspx", true); 
xhr.send(null); 
} 

function QuitPrealable() {


if ( nico=='FRM_PREALABLE' )
{
    AjaxQuitPrealable();
    nico=''
}
}
window.onbeforeunload = function() { QuitPrealable() };