[Typo3] how to change css

[bartek]

hello, my question is IF and if yes - HOW to change .css of the 
document. Can I do the link from the site, so if sb. click it, it 
changes on-the-fly .css used by site (my TYPO3 site is CSS Styled 
Content) by the parameter passed from the url (globalvar)?
regards Bartek