after another stretch of 10hours on the code:
W3C validation successfully done for: viewpage.php, loopsearch.php, profile.php, and all includes used in theese (that was debugging about 120 code typos there...)
Used firefox web developers tools to spot some more .CSS bugs, all cleaned
created DB ameta containing dynamic keywords & descriptions, included to head.php via ameta_include.php - brings individual meta-tags to each page.
finally found the encoding error that lead to so much question marks within the forum/faqs... just copy-pasted the spanish and portuguese faqs thru a encoder and gone the question marks are, even äs and ös are displayed propely to non germans. Little problem, lots of work.
still some .css cleanup to do until the last warnings will disappear, 404-page is still missing.
All aiming at better pageranking and more hits by search engines. lets hope it works :)