Hello we are also a webdesign company and we have site wide links in our clients websites but these websites are not related to our business. Should I nofollow these links?

Thanks

You can nofollow them so that the link value does not "leak" away from your site, that would make sense in fact.

As for these links harming you - they will harm you if Google finds out / decides that they are paid links. Also if there are really many of them and this isn't a blog roll that would be suspicious as well.

From my portfolio page I of course nofollow them but I mean should I nofollow them on my clients websites (footer links).

And what do you mean with "this isn't a blog roll"?

Thanks!

It could do you good to keep these links dofollow if possible. Links like "Designed by <..>" are so frequently used at the footers of web pages, that robots won't mistake them for paid ones.



Blogroll is a list of links to other blogs and sites a blogger frequently visits and/or recommends others to visit. You can find a blogroll on the homepages of most blogs. If you add a URL to this section of a blog, it won't be countered as an ad.