When I'm making a clients site I always include a link
<p>site by <a href="example.com" target="blank" rel="no follow"><strong>example</strong></a></p>
Is this bad practice from a SEO point of view, especially after the Google penguin update? Could this damage my clients site (the one hosting the link) and / or my site (the one that the link is pointing to).
Does making the link no follow get around the fact Google might deem the link to be a site wide spam link?