This is a stupid question, and I am aware that it is; but never the less, here it comes:
Is it possible to close a <script>-tag within itself, so to speak? I mean if you are using an external javascript-document can you close the tag like this:
<script type="text/javascript" src="xxx.js" />
As far as I am aware of it, no.
Browsers usually ignore self closing script tags.
If the document is XHTML served as XML, then yes, that's perfectly valid. If you're serving XHTML as HTML, however, it's not recommended as the SGML-style parsers that browsers use to processes tag-soup HTML may have a problem with it. (If you do decide to use self-closing script tags like that, be sure and test in several browsers first!)
Have a look at this topic http://stackoverflow.com/questions/69913/why-dont-self-closing-script-tags-work