Is a tag like the following supported in the editor:
<script language="javascript" src="somefilie.js"></script>

I have a client who must have gone into html mode, pasted this html in, saved ok, then when they try to edit it again the page seems to break (cannot save or do other things).  Testing makes me think it's the <script> tag.  Any ideas?

Also, is the upgrade from v3 to v4 seamless enough that a v3 install can be simply replaced with v4 and any existing custom pages (that pull in the editor and such) work the same?

Thanks,
Kevin