Object Unexpecter Error (javascript)

[YodaMan]

I keep getting this stupid error and I am not sure why. I was wondering if anyone could see an obvious mistake I made and point it out to me. It would be greatly appreciated.
It keeps telling me that this is the line with the error.

<TD >Phone Number: </TD>
<TD align=left width=200><input value="" type="text" onKeyDown="javascript:return dFilter (event.keyCode, this, '(###) ###-####');"></TD>


and this is what i wrote in the header

<script type='text/javascript' src='dFilter.js'>

 

[MrChad]

Can you post the code of dFilter()?

btw, your script tag should be closed:

<script type='text/javascript' src='dFilter.js'></script>