The “nofollow” attribute tells Google that the source being linked to cannot be vouched for. Basically it tells Google you DO NOT TRUST the content being linked to.
I did a quick check in my source code and found several instances of this attribute in the default CS-Cart code. The links were pointing to locations on my own site. Just wondering if these should be removed. Here is a quote from Google's own guidelines on the matter:
“If you can't or don't want to vouch for the content of pages you link to from your site - for example, untrusted user comments or guestbook entries - you should nofollow those links. This can discourage spammers from targeting your site, and will help keep your site from inadvertently passing PageRank to bad neighborhoods on the web.”
Do I really want to be telling Google I don't trust my own site?
For the realated links most probably.
Google won't think a site can not be trusted because of some nofollow links. Nofollow links can also simply be used so that no ranking is given to the page you are linking to, which might sometimes come in handy.
You should for example also use nofollow links for links you paid for like advertisements on other websites.
Additionally some links just lead to a dead-end for a robot like login page or switch languages. There are many uses of the nofollow attribute and it is completely advisory.