I'm trying to make a 404 error page.
I've successfully made it so that when anyone accesses a page on my site that does not exist they get sent to the 404 page but what i'm trying to do is that when the error page is loaded, an alert comes up saying "this pages does not exist...etc" and when the user presses the ok button, they are redirected to another page. it sounds so simple bt i'm not sure how to do it. anyone know how?

How about just placing the alert in an onLoad for the 404 page?

on the 404 error page place this in the head tag

<script language="javascript">
<!--
alert("THIS PAGE DOES NOT EXIST")
//-->
</script>