Thanks to all for your help!!
Arifin FinLy wrote:
Open your template index.php at:
<Joomla Root>/templates/<your template name>/index.php
...
Funny, this did it!!! Thanks a lot! Was it a problem with floats?
JEM wrote:
Again., without looking, you may want to try DocMan's Blog Theme.
main.mjaztools.com/downloads.html?task=cat_view&gid=20
It integrates nicely with most templates....
Thanks for this suggestion, unfortunately the layout problem persists, same as above.
Henning wrote:
As most of the things are surounded by a div of class dm_docs you should be able to tweak everything via css.
Sounds good! Thanks for your explanations, unfortunately this does not solve my problem.
After all I would like to solve it clean and without adding a table. As a link won't help you (you need to be registered and logged in to use docman), I provide you a screenshot.
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Please log in or register to see it.
If that's not enough I could send you the link and user-details via pm.
Thanks a lot in advance!!! 
DW