if (!document.all)//non-ie
{  
    window.onbeforeunload = function()
    { 
        Sys.WebForms.PageRequestManager.getInstance().add_endRequest(ignoreOnEndRequest); 
    }

}

function ignoreOnEndRequest(sender, e) 
{   
     err = e.get_error();    
     
     if (err)   
      {     
         if (err.name == "Sys.WebForms.PageRequestManagerServerErrorException")       
         {        
            e.set_errorHandled(true);      
         }    
         
         else if (err.name == "Sys.WebForms.PageRequestManagerParserErrorException")       
         {        
            e.set_errorHandled(true);      
         }    
      }  
 }