StackOverflow Solution

window.onload = function(){
var preElements = document.getElementsByTagName('pre');
var codeLine = new Array();
var newContent

for(var i = 0; i < preElements.length; ++ i)
{
    var element = preElements[i];
    newContent='<table width="100%" border="1" cellpadding="0" cellspacing="0" >'

    codeLine = element.innerHTML.split('\n');

    for(var j=0 ; j < codeLine.length ; j++){
        newContent = newContent + '<tr><td width = 30 class="codeTab1" >' + j.toString() + ' </td><td class="codeTab2"> ' + codeLine[j] + '</td></tr>';
    }

    newContent = newContent + '</table>';
    element.innerHTML = newContent;


}
}