Do people think it's best to make internal links to unimportant seo landing pages (eg contact page, site map) nofollow or dofollow? I can remember reading a seo book a year or so ago now that claimed that internal links from the home page do not drain the link juice from the home page but recently - in another forum - I came across a couple of people thinking that links to pages such as the cotnact page should be nofollow. Would appreciate any thoughts.

You may have opened a can of worms on this one! I do use nofollow on internal links and have had numerous debates about the issue over the last year.

The nofollow tag started out as a way of discounting paid for and unsolicited links but SEOs quickly realised that it could be used to control the flow of pagerank internally. Since that practice appeared Google havent said too much about it but (as boogaloodude cited) matt c did say "There's no stigma to using nofollow, even on your own internal links". So that's good enough for me! I've been using it on client sites to pagerank sculpt and so far non of the sites have been penalised.

For a webmaster who isnt confident in what theyre doing with nofollow I'd recommend some basic structural use on registration links, login links, privacy page links etc. If you leave these pages unblocked then they take pagerank which could have gone to more important pages.

To clarify in the simplest way possible... You have a 3 page site:

home page --> product/service page
                --> login page

When NO nofollows are in place the pagerank passed from the home page is split between the product and login page. But when you add a nofollow to the login page link the pagerank that the home page gives is channelled FULLY through to your service/product page... So in theory that page gets more pagerank. It's a pretty sound theory. If it wasnt a sound theory one of the initial intentions of using nofollow (to stop pagerank flow to blog spammers and advertisers) would have failed.

If you know what youre doing you can use nofollow to sculpt the entire sites's pagerank and send more of it to the pages youre trying to rank. For example, people say "put no follows on your contact us links" -- not recommended if people search for your contact details. I personally would never block a contact page! But you could block some of the links to it so it is less of a pagerank stealer.

One factor i'd also like to mention which relates to large sites and may answer the "pagerank doesnt matter" critics... If you have a site with low pagerank the more pages you add to that site the more that small amount of pagerank is divided amongst those pages. When that pagerank gets too low the page is tossed into the supplemental index (other factors are involved). If a page is in the supplementals then the chances of it appearing for a competitive search are very low. Specific/longtail searches maybe but not for anything slightly competitive. So for that reason it makes sense to block all pages that dont require pagerank/rankings and give it to the ones that do.

One aspect that I am still investigating is whether blocking a page in the robots file results in it being dropped from the pagerank calculation or does it still build pagerank? If it does then blocking a page in robots but not blocking it's internal inbound links is a sure fire way to waste pagerank...

True, but he also said:  "we don't generally encourage this behavior"

and:

"My analogy is: suppose you’ve got $100. Would you rather work on getting $300, or would you spend your time planning how to spend your $100 more wisely.

Spending the $100 more wisely is a matter of good site architecture (and nofollowing/sculpting PageRank if you want). But most people would benefit more from looking at how to get to the $300 level."

I rarely use the nofollow attribute on internal links on my sites, but I do see that at least in theory PR sculpting is possible. But I do use nofollow on 99% of our outbound links because most of the outbound links are to advertiser web sites.

I think the last time I used it on an internal link was because the Yahoo bot exhibited some bad behavior by hammering a few query forms and leaving those queries open, and that would lock up MySQL.

On our sites there really aren't too many pages I would block anyway. Also, since most of our sites are Joomla sites if I used the Joomla menu module system I would have to rewrite some of the core code so I could call up the nofollow attribute when it was needed.

Does anyone have any actual before and after data and results from implementing PR sculpting on their sites?

But, when have you read what google or matt c suggests with anything less than a pinch of salt?! Unless they say "dont do this or we will penalise you" im generally gonna put their advice down to subtle rhetoric to encourage me to build a better sites - which would make me a webmaster more than an seo -- who's primary role is to optimise whats already there.

If a link isnt nofollowed, it takes pagerank. But that doesnt mean that you should nofollow everything that isnt in the main menu -- just makes sure that your whole site structure generally links to your most important pages most. So the links that you feature in your content should link to your best pages and that tells google "hay, i link to this page more than the others therefore its a better page and should get more of my pagerank!"...

Xenu is a great free tool for checking out your site linking...

Totally agree with Boogaloodude

Yep, youre right... I meant if a link isnt nofollowed (or blocked in some other way) then it takes PR to the destination page, should have been clearer...