if ( window.addEventListener ) {
window.addEventListener("load", function(){sendPb(url);}, false);
} else if ( window.attachEvent ) {
window.attachEvent( "onload", function(){sendPb(url);} );
} else if ( window.onload ) {
window.onload = function(){sendPb(url);};
}
原文：http://www.cnblogs.com/wzktravel/p/4030888.html