Google suggests: "nofollow" - what about rel='external nofollow'?

[Bambarbia]

rel="nofollow" was initially suggested by Google, it is unapproved de-facto hint for search engines.

I am mostly software engineer and very new to SEO. I noticed in Webmaster Tools external links to my site which have rel='external nofollow'.

As a sample: Regular Expressions are used in most engines at least for checking META tags before XML/HTML parsing. And some have hard-coded and hacker-unsafe values (attributes are in specific order; it can't understand META with attributes in different order) and etc. May be Google understands rel="nofollow" and does not understands rel='external nofollow'? I checked source code of Nutch, it has similar bugs.

"nofollow" has a meaning to "not automatically crawl linked page". What if that linked URL is already in a database?

Indeed, "in-topic" links should count for PageRank/TrustRank.

[tedster]

external links to my site which have rel='external nofollow'

That is a standard way of giving an attribute more than one value - Google should not have a problem. And if they do, it just means your page will get the backlink power, nothing more.

What if that linked URL is already in a database?

The rel attribute is only specific to the link where it appears. If there is any other link to your page (either on your site or external to your site) then your url is crawled and given backlink credit.

Here's a recent discussion with some more information. Our Site Search [webmasterworld.com] will locate several other threads as well.
[webmasterworld.com...]