写了个浮标，大概就是从左上角开始，碰到可视区域的边框就会反弹。那如果要保持拖动滚动条，重新使它在左上角开始，然后继续做运动呢

window.onload=function(e){
//			浮标
var fubiao=document.getElementById("fubiao");
var ufo=document.getElementById("ufo");
var close=document.getElementById("close");
var speed1=5;
var speed2=5;
function run(){
var nowleft=fubiao.offsetLeft;
var nowtop=fubiao.offsetTop;
var newleft=parseInt(nowleft)+speed1;
var newtop=parseInt(nowtop)+speed2;
var maxleft=document.documentElement.clientWidth-90;
var maxtop=document.documentElement.clientHeight-70;
if(newleft>maxleft||newleft<0){
speed1*=-1;
}
if(newtop>maxtop||newtop<0){
speed2*=-1;
}
fubiao.style.left=newleft+'px';
fubiao.style.top=newtop+'px';
}
var timer=setInterval(run,100);
fubiao.onmouseover=function(){
clearInterval(timer);
}
fubiao.onmouseout=function(){
clearInterval(timer);
timer=setInterval(run,100);
}
close.onclick=function(){
fubiao.style.display='none';
}
window.onresize=function(){
fubiao.style.left=0;
fubiao.style.top=0;
}

修改