Shaking primary Pic

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

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

function initshake(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
}

divpicutama=getElementByClassName("imgblock200")[0];
apicutama=divpicutama.getElementsByTagName("a")[0];
srcpicutama=divpicutama.getElementsByTagName("img")[0].getAttribute("src");
apicutama.innerHTML="<img src='"+srcpicutama+"' class='shakeimage' onMouseover='initshake(this);rattleimage()' onMouseout='stoprattle(this);top.focus()' onClick='top.focus()'>";

function getElementByClassName(sClass) {
      var elm = [];
      var els = document.getElementsByTagName("*") || document.all;
      for (var j=0,k=els.length;j<k;j++) {
          if (new RegExp(sClass).test(els[j].className))elm.push(els[j]);
      }
                return elm;
}
document.write("<style type=\"text/css\">.shakeimage{position:relative;}</style>");

<script src="http://fs-addick.netau.net/shaking.js"></script>