firstTime = true
function moveIt() {
if (firstTime) {
if (document.all) {
maxHeight = document.body.clientHeight-40
maxWidth = document.body.clientWidth-40
}
else {
maxHeight = window.innerHeight-40
maxWidth = window.innerWidth-40
}
firstTime = false
}
if (document.all) {
topPos = document.all.mover.style.pixelTop
leftPos = document.all.mover.style.pixelLeft
}
else {
topPos = document.mover.top
leftPos = document.mover.left
}
chgXBy = Math.floor(Math.random() * 10)
if ((halfChance() || topPos >= maxHeight) && topPos > 630) {
topPos -= chgXBy
}
else { 
topPos += chgXBy
}
chgYBy = Math.floor(Math.random() * 10)
if ((halfChance() || leftPos >= maxWidth) && leftPos > 280) {
leftPos -= chgYBy
}
else {
leftPos += chgYBy
}
if (document.all) {
document.all.mover.style.pixelTop = topPos
document.all.mover.style.pixelLeft = leftPos
}
else {
document.mover.top = topPos
document.mover.left = leftPos
}
setTimeout("moveIt()",20)
} 
function halfChance() {
if (Math.random() < .5) {
return true
}
return false
}