function zebra(){
// define used variables
  var momtable,mombodys,i,j,addclass,colourclass;
// define the class to add to colourise the rows
  var colourclass='colouredrow';
// grab the table, and each tbody in it.
  momtable=document.getElementById('classinfo');
  mombodys=momtable.getElementsByTagName('tbody');
// loop through the rows of the bodys
  for (i=0;i<mombodys.length;i++)
  {
   momtrs=mombodys[i].getElementsByTagName('tr')
   for (j=0;j<momtrs.length;j++)
   {
// if the rows don't contain any headers
    if(momtrs[j].getElementsByTagName('th').length==0)
    {
// add the class colourclass to each second row.
     addclass=j%2==0?' '+colourclass:'';
     momtrs[j].className=momtrs[j].className+addclass;
// call the function hlrow 
     momtrs[j].onmouseover=function(){hlrow(this);};
     momtrs[j].onmouseout=function(){hlrow(this);};
    }
   }
  }
 } 
 function hlrow(o)
 {
// check if the row's classname already contains hl and replace respectively 
// add it.
  o.className=/hl/.test(o.className)?o.className.replace('hl',''):o.className+' hl';
 }
 
 if(document.getElementById && document.getElementsByTagName)
 {  
  //window.onload=zebra; 
    }