How can I tell if a site is trustworthy and is not / hasn't been penalized by Google?

[CosminC]

Hello Moz Community,

I'm looking to do some link building for a client and I would like to know if there's a way to find out if a website is trustworthy and is not or hasn't been penalised by Google.

Thank you.

[Kenn_Gold]

I usually just use the Moz Rank score here using Open Site Explorer.   http://moz.com/learn/seo/mozrank

[Ham1979]

tools on moz and other sites to see who links to the site as well as seeing if they're ranking well for the keywords you would associate with them. If they've got a penalty they probably won't rank that well

[Linda-Vassily]

You could do a search using site:domain.com and see what (if any) pages Google has indexed for the site; if there are none, that is a bad sign.

You could also put the domain's URL in Open Site Explorer and take a quick look at the types of links the site has. (I myself have the Moz toolbar installed in my browser so when I go to a site I can quickly get an idea of its authority.)