Before messing with the DOM (document.[...]), it might be smart to wait for the HTML doc to be fully parsed and the DOM tree to be fully built. This can be achieved as follows:
<script type="text/javascript">
function my_dom_manipulator1() { ... }
function my_dom_manipulator2() { ... }
function my_dom_manipulator3() { ... }
// Execute our snippets after the page is parsed.
var old_onload = window.onload;
window.onload = function() {
if (old_onload != null)
old_onload();
my_dom_manipulator1();
my_dom_manipulator2();
my_dom_manipulator3();
};
</script>
For an example of where this makes a difference, refer to Free Nodelet Hack: Nodelets on the left.