How to find out which js code changes selected index
<p>I have a dropdown and my selected index is set by php (which works as long as javascript is disabled).</p>

<p>When i enable javascript, then my selected index is changed to the first option as soon as the page is loaded. Now i need to find out which piece of js changes my selected index.</p>

<p>Can anyone tell me please how to find this out, for example by using firebug?</p>