I am trying to make an extension as part of which i want certain words in the web pages to be highlighted. The document.body.innerHTML.replace() replaces the url in the address bar as well. So the moment this code gets exwecuted the page doesnt get loaded properly.. Is there a way around this problem?

onPageLoad: function(aEvent) {  
       var doc = aEvent.originalTarget;
        var str="the";
 var regex;
 var regex = new RegExp(str, "g");
    doc.body.innerHTML = doc.body.innerHTML.replace(regex,'<b>'+str+'</b>');
}

The listener is registered as follows in a browser.xul overlay:

window.addEventListener("load", function() {
  myExtension.init();
}, false);
var myExtension = {
  init: function() {
    var appcontent = document.getElementById("appcontent"); // browser
    if(appcontent)
      appcontent.addEventListener("DOMContentLoaded", myExtension.onPageLoad, false);
  },