效果收集-滚到一定程度再漂浮

window.onscroll = function(){
var t = document.documentElement.scrollTop || document.body.scrollTop;
var Div = document.getElementById( "fix_goods" );
if( t <= 755 ) {
Div.style.position = "";
Div.style.top = "";
} else {
//Div.style.display = "none";
Div.style.position = "fixed";
Div.style.top = "-10px";

}
}