Warning: Please include a link to the DD script in question in your post. See this thread for the proper posting format when asking a question.
The problem is that your initialization code is within the same SCRIPT tag that also references the external .js file. They should be separate, so:
Code:
<script type="text/javascript" src="dateien/ddtabmenu.js">
/***********************************************
* DD Tab Menu script- Đ Dynamic Drive DHTML code library (www.dynamicdrive.com)
* This notice MUST stay intact for legal use
* Visit Dynamic Drive at http://www.dynamicdrive.com/ for full source code
***********************************************/
</script>
<script type="text/javascript">
//SYNTAX: ddtabmenu.definemenu("tab_menu_id", integer OR "auto")
ddtabmenu.definemenu("ddtabs", auto) //initialize Tab Menu #3 with 2nd tab selected
</script>
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