Comment on Rel Nofollow by SEO Dave.
Dofollow clickable image links, as above.
Nofollow clickable text links pass no SEO benefit, deletes the PR/link juice that would have been passed if the link was dofollow.
Nofollow clickable image links as above.
Body text link, non clickable (like www.example.com) is not a text link, has no SEO impact PR/link juice wise. Will be treated as body text.
<span class="affst" title="tests" id="http://stallion-theme.co.uk/">Stallion Theme</span>
Many link cloaking scripts use clickable text links that 301 redirect to the URL, the sort that use www.example.com/go/here/ and redirect to another page (many affiliate marketers use this type of link cloaking) are treated as clickable dofollow text links, so they pass full SEO benefit minus a small dampening factor that’s added to 301 redirects.
All recognisable clickable links receive a fair share of the link benefit available from the page, if there’s 1,000 PR points (arbitary unit for calculation reasons) available from your average PR5 page and there’s 10 clickable links from the page, each clickable link (whether nofollow or dofollow) will use 1/10th of the PR points and with 1,000 PR points available each will receive 100 PR points (1,000 divided by 10). Another example 1,000 PR Points 50 clickable links from the page, each receive 1/50th or 20 PR Points (1,000 divided by 50). If your average PR4 page has 300 PR Points you can see less PR points are passed per link.
Quick way to estimate PR Points at SEO Tutorial – PageRank (PR)
You can see how much damage a particular nofollow link causes depends very much on the page the nofollow link is on.
A page PR2 page with 300 dofollow links and one nofollow link isn’t worth worrying about.
A PR7 page with 5 dofollow links and 15 nofollow links is a major problem, that page would be deleting 3/4s of it’s PR and as it’s PR7 that’s a lot of wasted link juice.
It’s irrelevant whether we think it makes sense the link juice of nofollow links is deleted, doesn’t make sense to me, but Google via Matt Cutts has confirmed this is how Google works, it’s as close to an SEO fact (Matt Cutts could be lying I suppose) you get with Google SEO.