Step 1: Insert the below into the <head> section of your page:

<style>
.shakeimage{
position:relative
}
</style>
<script language="JavaScript1.2">

/*
Shake image script (onMouseover)-
© Dynamic Drive (www.dynamicdrive.com)
For full source code, usage terms, and 100's more DHTML scripts, visit http://dynamicdrive.com
*/

//configure shake degree (where larger # equals greater shake)
var rector=3

///////DONE EDITTING///////////
var stopit=0
var a=1

function init(which){
stopit=0
shake=which
shake.style.left=0
shake.style.top=0
}

function rattleimage(){
if ((!document.all&&!document.getElementById)||stopit==1)
return
if (a==1){
shake.style.top=parseInt(shake.style.top)+rector
}
else if (a==2){
shake.style.left=parseInt(shake.style.left)+rector
}
else if (a==3){
shake.style.top=parseInt(shake.style.top)-rector
}
else{
shake.style.left=parseInt(shake.style.left)-rector
}
if (a<4)
a++
else
a=1
setTimeout("rattleimage()",50)
}

function stoprattle(which){
stopit=1
which.style.left=0
which.style.top=0
}

</script>


Step 2: Add the below inside the <img> tag of all of the images you want the effect applied to:

class="shakeimage" onMouseover="init(this);rattleimage()" onMouseout="stoprattle(this);top.focus()" onClick="top.focus()"

An example would be:

<img src="baby_blocks.gif" class="shakeimage" onMouseover="init(this);rattleimage()" onMouseout="stoprattle(this);top.focus()" onClick="top.focus()">