[TYPO3] CSS styles only working with tt_content?!

[Kanu- und Ski-Club Lünen e.V. - Thorsten Dorn]

Hello everybody,

I managed to move my page to CSS use, by use of the CSS Styler. I  
created a file that carries all of the sytles centrally. Every time I  
edit it with the CSS Styler the file changes/extends successively. So  
for so good, but only tt_contents adopt the changes. None of the  
FORMS on my page change, even though I defined styles for them in CSS  
Styler. Also some EXTENSIONS don't accept CSS changes, like e.g. the  
Modern Linklist. So here ist my question: How can I tell extensions  
to make use of the style sheet? Some exemplary code is mostly very  
helpful for me. Could not find an answer in the Matrix...

Many thanks,
Thorsten