if (typeof (Sys) != 'undefined')
{
  Sys.WebForms.PageRequestManager.getInstance ().add_beginRequest (beginRequestHandler);
  Sys.WebForms.PageRequestManager.getInstance ().add_endRequest (endRequestHandler);
}

function beginRequestHandler (sender, args)
{
  document.body.style.cursor = 'wait';
}

function endRequestHandler (sender, args)
{
  document.body.style.cursor = 'default';
}