Hello,
i build a drupal website and use the fckeditor. I tested my website with the html validator from http://www.w3c.org. There are 2 Errors i get because of the FCKEditor. When i insert a image on the right side of the text the fckeditor post the following code:
<img width="800" height="600" align="right" src="/image.jpg" alt="" />
Re: FCKEditor not XHTML Strict valid | align is not allowed.
It can be done
You must replace align attribute with class attribute and maybe write some new classes to youre css file... I use fckeditor + Drupal and I looked the same solution. Now I got working example. http://kutotootmine.ee Next problem will come up with tables 
This I havent done yet but it will work the same way I guess.. 
... If you need same solution you can let me a note http://web3.ee/contact
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21.May 2009 Table problem is solved long time ago for now