why must the script in header and not an external script

[Mgccl]

your table widget is great, I found to put scripts in the header makes each page seems some kbs larger.
so I tried to make it into
<script type="text/javascript" src="tpl/js/highlight_table.js"></script>

but sadly, it does not work

it must be in the header, can't be external...

is there a way to make that work even I make it external?
btw I'm using Opera...

[Batalf]

[Mgccl]