代码复制区

第一步,在<body>与</body>之间加入
<script>
<!-- Beginning of JavaScript -
var x,y
var marginbottom
var marginleft=0
var margintop=0
var marginright

var cliptop
var clipbottom
var clipleft
var clipright
var clippoints

var ballheight=150
var ballwidth=150

var imageheight=280
var imagewidth=580

// less is faster
var tempo=25

// horizontal move (pixels) within time unit
var stepx=12

// vertical move (pixels) within time unit
var stepy=6
var timer

// check the width and the height of the document
// gets the starting position of the ball by random
function setValues() {
	if (document.all) {
    	marginbottom = imageheight-ballheight
    	marginright = imagewidth-ballwidth
		document.all.ball.style.posLeft=randommaker(400)
   		document.all.ball.style.posTop=0
		document.all.textcontent.style.posLeft=0
   		document.all.textcontent.style.posTop=0
			document.all.ball.style.filter="alpha(opacity=0,finishopacity=100,style=2,startX=0px,startY=0px,finishX=100px,finishY=100px)"
    	moveball()
	}
}

// randomfunction
function randommaker(range) {
	rand=Math.floor(range*Math.random())
    return rand
}

function moveball() {
	checkposition()
	if (document.all) {
   		document.all.ball.style.posLeft+=stepx
   		document.all.ball.style.posTop+=stepy

cliptop=document.all.ball.style.posTop
		clipbottom=cliptop+ballheight
		clipleft=document.all.ball.style.posLeft
		clipright=clipleft+ballwidth

clippoints="rect("+cliptop+" "+clipright+" "+clipbottom+" "+clipleft+")"
		document.all.textcontent.style.clip=clippoints
    	timer=setTimeout("moveball()",tempo)
	}
}

第二步,在<body>中加入onload=setValues()