I am assuming that you want to benchmark the performance by measuring the load time for a given page.
This can be accomplished fairly easily by using something like the following code.
Place this right after the body tag:
Then place this as close to the closing body tag as possible:
var msecs_start = new Date();
You will then see a number enclosed within bracket which gives you the load time. There are probably more elegant (and more accurate) ways to achieve the same affect, but this should at least give you an idea.
var msecs_stop = new Date();
var diff = (msecs_stop.getTime() - msecs_start.getTime())/1000;
document.write('<span class="fright">[<a href="java script:void(0);" title="This page took ' + diff + ' seconds to load.">' + diff + '</a>]</span>');
You can check out this web site for a working example.
Is this what you meant?