[Marco van Herwaarden]

Maybe that is because your signature is not within our rules:

4. Signature Rules

4.1 Size Limits: All signatures should not exceed the following size limits:
Just Text: 8 lines small size or 4 lines size 2 and up to 90 chars per line
Just Image: 1 image up to 300 pixels wide, 125 pixels tall and 20k in size
Text and Image: 4 lines (or 2 with Textsize 2) and one image (in a new line) up to 300 pixels wide, 75 pixels tall and 20k in size.
( Empty lines are counting as well.)

4.2 Content restrictions You may have a link to your own website or services, but there must be no promotional language like "Best Hosting" or "Cheapest Styles". Paypal and affiliate links are NOT permitted.

Dynamic scripts linked in signatures that attempt to create cookies in another person's browser are not allowed for security reasons and will be removed.

As an addition: You cannot use [color] tags in signatures, if you want to highlight something you can use the [high] tag.