[TYPO3] How to get rid of tx_veguestbook_pi1 styles (or make them valid)

[Michael Baker]

I have in the past used tx_veguestbook_pi1 but have, I thought, removed 
all references to it on my website.  However it still puts styles in the 
header on every page.  Either how can I get rid of them or change them 
so that they are valid CSS?  I'd RTFM if I knew which F manual to read - 
please point me in the right direction.

Uninstalling the guestbook is not an option as other websites located on 
the same Typo3 database use it.

Michael.