自由移动的图片的特效

<img src="http://code.helpor.net/picture/swimming.gif" name="u" border="1" alt="很好玩的">
<script language="JavaScript">

var b = 1;
var c = true;

function www_helpor_net(){
if(document.all);

if(c == true) {
b++;
}
if(b==100) {
b--;
c = false
}

if(b==10) {
b++;
c = true;
}

if(c == false) {
b--;
}
u.width=150 + b;
u.height=125 - b;
setTimeout("www_helpor_net()",50);
}
www_helpor_net();
</script>