When jQuery is looking for an element by the "id" attribute, it uses the browsers native document.getElementById() method, as it is extremely fast.

However due to a bug in IE (also mimicked in Opera), elements with a name attribute matching the id, that appear above the true element (matching the id) in the DOM are returned.

jQuery catches this already, and does a check to see if the (tmp.id != id) if the element is a bogus match (e.g. due to the bug), it then does AFAIK, a 'deep' query checking all elements for a match on the id attribute.

If this is so, then there is a potentially huge performance increase, by implementing the following.

Rather than do the deep query, execute a one-time fix for IE & Opera, to correctly return the first element matching by ID.

IE has a proprietary array on the document called "all", under normal circumstances I would never suggest using it, but in this scenario it is helpful. For every element added to the DOM, with an "id" or a "name", IE adds a named reference to the document.all associative array.

This means, that if you had say, a meta tag, with name="description" and a form element, with id="description" that document.all['description'] would be an array with [meta element, form element]. Since IE has these references cached, pulling them from this dataset is VERY FAST.

The following code would likely need to be re-jigged to match the jQuery format, but essentially this works, by re-mapping the method, to return the correct thing.

//fix both IE and Opera (adjust when they implement this method properly)
if(jQuery.browser.msie||jQuery.browser.opera){
  document.nativeGetElementById = document.getElementById;
  //redefine it!
  document.getElementById = function(id){
    var elem = document.nativeGetElementById(id);
    if(elem){
      //verify it is a valid match!
      if(elem.id == id){
        //valid match!
        return elem;
      } else {
        //not a valid match!
        //the non-standard, document.all array has keys
        //for all name'd, and id'd elements, and querying
        //it is FAST!

        //start at one, because we know the first match, is wrong!
        for(var i=1;i<document.all[id].length;i++){
          if(document.all[id][i].id == id){
            return document.all[id][i];
          }
        }
      }
    }
    return null;
  };
}