1. changing colors of a link...
i have this code:
"{style:type=div|align=left}*{style:type=span|font-size=12px|color=#ffffff|background-color=#DE2626}[Review product feedback to designers>Rev_Desfeed]{style}*{style} "
it worked fine before i made it a link:))) now i have no idea how to control the colors. i saw something on the internet about using css.. i have used css so far but in xwiki i think i don't get it.

You can use CSS. the color attribute targets text color. To change a link color you need to target the <a> element using something like <style> a {color: #000;} </style>

2. i wanna merge 2 cells of a table . do ya have any idea how to do that...
and another thing..is there something like a forum for xwiki, or a website where all the questions have been answered can be found there? so that i won't ask question that were already asked.:)

AFAIK XWiki doesn't support cell merging as of now. However you can combine the table macro with html to create merged cells, as in http://www.xwiki.com/xwiki/bin/view/Solutions/Subscription?viewer=code -> look at how the table is written.

You'll find a lot of info here : http://www.xwiki.org/xwiki/bin/view/FAQ/ . Please take the time to add new entries there once you find answers to your questions.

Thanks,

Guillaume