How to check if you have a Google penalty

[Bamikanarie]

We're doing a SEO run on some of our sites, but we have the feeling we may have received a penalty on some of our domains. The problem is: how do you tell? We have no history on the ranks we had before, and our field of keywording is highly competitive.

So can anyone shed some light on how one can check if a site is penaltilized? Is there a tool somewhere, or a hint in Google Webamsters?

This also implies the question: how do you see what's your result page position if your not in the top 20 pages (eg: when starting work on a new site)

[tedster]

First thing I would do is set up a Webmaster Tools account and validate the domain. See if Google responds with a message about a penalty or problem -- they often do.