Welcome to the Q&A Forum

yes, one website with subfolders is definitely best.

https://www.moz.com/  has an invalid cert guys

This Connection is Untrusted

You have asked Firefox to connect
securely to www.moz.com, but we can't confirm that your connection is secure.
          Normally, when you try to connect securely,
sites will present trusted identification to prove that you are
going to the right place. However, this site's identity can't be verified.

What Should I Do?

If you usually connect to
this site without problems, this error could mean that someone is
trying to impersonate the site, and you shouldn't continue.

www.moz.com uses an invalid security certificate.

The certificate is only valid for moz.com

(Error code: ssl_error_bad_cert_domain)

If you understand what's going on, you
can tell Firefox to start trusting this site's identification.
Even if you trust the site, this error could mean that someone is
tampering with your connection.
          Don't add an exception unless
you know there's a good reason why this site doesn't use trusted identification.

6000 pages sounds like improper pages are getting indexed, unless you have 6000 articles which i doubt.

I would block the /tag/ and /category/ and /2013/ type of folders. Yoast plugin will do that for you. Then you're down to just content. If the anchor texts are overdone that could hurt you and I would disable the incontent interlinking if it's overdone for SEO. Then you're left with compliant pages that won't hurt your site, and if it's content that is unique and not spun type of junk I would just leave it on the site since extra content on the site is a good thing, even if the blog posts aren't generating much traffic or ranking. It could be linked to less prominently on the site like in the footer so that less PR is getting passed to it and users aren't visiting it as much from the main pages. Users and PR is staying focused on the main site.

Paid to put them up and paid to remove them, amazing isn't it.

It really depends on how toxic the links are, what your link profile looks like, if you are trying to recover from a penalty and how much money your site generates. I have paypalled people many times to remove links for me for their "coding time" but i've usually reached out offering via email and offered instead of people telling me I have to pay.

If the link is on a horrible site and sitewide for instance it might be worth it to pay to get that link down.

It is only one of several factors Google could take into account. Same registrar owner, interlinking, shared assets etc are all factors used by Google to determine having more than one horse in the race for same keyword targets. If hosting location is the only interconnectivity you're probably alright, but if the site is completely nuked and you're phasing it out you might just want to noindex it and then you will automatically be fully compliant.

you can put a chunk of content on the page like in the sidebar or footer so you can get a couple instances of the main keyword on the homepage which always remains there regardless of whether the latest blog posts contain that content or not. Also, in the homepage image file name, meta description, h1 or wherever else it's approproate to add it without overdoing it of course.

The site features tens of thousands of profiles. Profile owners can purchase sponsored links that will feature their  profiles in strategic sections of the sites. These links can be featured on internal search results, related profile pages and on the top of the directory listings. The only reason their links are displayed is because they bought into the program.

Your listing pages should definitely have the prev and next tags. These tags were created for pagination. There are other solutions on how deal with pagination, but this is the one that Google recommends .  The bigger question for you is if you see value in Google indexing the listing pages and what possible landing page traffic you can expect from these pages. Without much index value, I would suggest adding a noindex, follow tag to your listing pages and avoid a potential Panda penalty.

I am having an internal debate on the need to use nofollow tags on sponsored internal links that link to internal pages. One thought is based on this Matt Cutts video  (Should internal links use rel="nofollow"?) in which he says that there is never a need to use a nofollow tag on an internal link. The other school of thought is that paid links with follow tags are a violation of Google policy and it does not matter if they link internally or externally. Matt was just not thinking of this scenario in his short video. Would love to hear if anyone has had any manual action from Google based on their internal links.

I see it's a problem with this tool

http://www.feedthebot.com/tools/spider/test.php?url=www.rocksolidroof.com

but I see the content recognized in Google

https://www.google.com/#sclient=psy-ab&q="even+thousands+of+dollars+on+future+repairs.+It’s+in+your+best+interests+to+make+sure+the+job+is+done+right+the+first+time"&oq="even+thousands+of+dollars+on+future+repairs.+It’s+in+your+best+interests+to+make+sure+the+job+is+done+right+the+first+time"&gs_l=hp.3...15397.28142.1.28370.129.45.0.0.0.0.0.0..0.0...0.45...1c.1.17.psy-ab.xiyDHYgHrec&pbx=1&bav=on.2,or.r_cp.r_qf.&bvm=bv.48293060,d.bmk&fp=6ef9c55ffbdd7e46&biw=1920&bih=910

If you're going to spam then use  www.example.com because if that anchor text gets suppressed no one is typing that in anyway to find you.

homepage is indexed under both www and www versions

"underfloor heating" too many times on the homepage, bolded, hyperlinked, etc. it's overdone

keyword stuffing

<meta name="<a class="attribute-value">description</a>" content="<a class="attribute-value">Underfloor Heating provided by underfloor heating company UFH1\.  
Suppliers and installers of underfloor heating kits based in Doncaster. Our underfloor heating systems are installed throughout the UK.</a>" /> <meta name="<a class="attribute-value">keywords</a>"
 content="<a class="attribute-value">underfloor heating, underfloor heating kits, under floor heating, underfloor heating systems, underfloor heating, UK</a>" /> 

Yes but make them noindex,follow -  not noindex,nofolllow

There is a slight chance that the footer link is encrypted and removing it will break the formatting of the theme. Just a heads up, if you see that happen you'll need to do a little bit of Googling and you will find the solution, it's only slightly tricky if you know programming.

Yes, intentional move by Google. People were selling links with tier based pricing based on PR.

Do you know if SEOmoz was www or non www because:

http://seomoz.org is 301 redirecting to http://www.seomoz.org

and http://www.seomoz.org is redirecting to http://moz.com/

http://seomoz.org should probably be 301 redirecting to http://moz.com/ to avoid that second hop. If the site was non www they could be losing PR being passed to the new domain.

I completely agree with Dan's advice - he just gave you like a grand of free research and advice.  Age doesn't matter - you need to clean up bad links from the past.

As long as the path is crawlable that extra folder has absolutely no benefit or any negative effect on SEO. Keywords in folder name / URLs to not help push rank.

I was easily able to find spam links (http://www.insignifica.org/linksblog/2010_04.shtml), so I suggest you review all your backlinks and disavow and try to remove them.

feel free to thumbs up    good luck!