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Social Bookmarking does still work but not as well as it may have in the past. It can still be a viable way to get traffic to your site but not necessarily always the most qualified traffic. Personally I'd say to stay away from any social bookmarking tools that will automate things for you because that will be a bit of a red flag if you're too spammy with adding your links. A more natural approach to getting your pages added to social bookmarking sites is the better way to go. Just don't expect it to magically increase you rankings, conversions, etc.

Assuming I fully understand your question, here's an example as an explanation: If Page A has 2,000 words and Page B has 500 but the bulk of Page B's content appears in Page A, then Page B is a subset of Page A's superset and should have a canonical tag pointing to Page A.

That can depend on the theme of your Wordpress site. Can you post a link to your site so we can take a look?

If you're 301 redirecting everything to proper, relevant alternative pages on the other site then there's no reason to canonicalize the page.

The Rel="Canonical" notice has nothing to do with changing your title tags... likely just a coincidence. Its not really an error either. All the SEOMoz crawler is doing is notifying you that the page has a canonical tag on it. Though I don't see a canonical tag on the link you posted above so I don't know why that page would have been listed unless it had one once and has since been removed.

It's usually suggested that Tag archives and Category archives be set to NoIndex which will help in alleviating this issue.

Would you mind posting a URL so people could take a look at the pages in question?

I'd assume GWT is returning a Soft 404 for those pages. Have you considered writing content for the page to express the need to log in for users to reach whatever important content is available via an account? That way Google sees that it is a real page and not so empty as to make them think it has 404'd. Or if there is no reason for Google to be indexing this page in the first place you could mark it NoIndex.

Ah... Googlebot can't see those changes on the page from when you click the different offers so each page looks almost exactly the same and like thin content. In which case I'd suggest something along the lines of adding more written content to pages like _http://www.ofertasdeemail.com.br/desconto/submarino/_ so they look different than page like _http://www.ofertasdeemail.com.br/desconto/submarino/so-o-cartao-submarino-indica-as-melhores-ofertas-para-voce-10733.html_ and then adding a canonical tag to show that the offers are a subset of _http://www.ofertasdeemail.com.br/desconto/submarino/_

They only problem with this solution is that the individual offers won't really rank for anything in the SERPs and will likely be replaced by the primary page in the index (assuming Google follows your canonical signal). So that may not be a perfectly solution for your needs but it could alleviate problems associated with duplicate & thin content.

First, determine if those duplicate content pages need to exist or if your users would be better served by another page. If that page doesn't need to exist then you may want to consider a 301 redirect to the better page. If a page is an exact replica of another page then you need to ask yourself "Why do we have it?" If its only a duplicate because of thin content then you might want to consider adding more, relevant content to the individual pages to better differentiate them.

If the duplicate page needs to stay for whatever reason then you can consider adding a canonical tag pointing to the primary page. Some cases in which canonicals have worked best on the sites I work on have been relating to parameters. E.G. example.com/product and example.com/product?model=4 are basically the same page but they each serve a purpose. In this case, example/com/product?model=4 is a subset of the one without a parameter and was given a canonical tag pointing to the primary page.

Canonical tags are a signal, not a directive though... which means that the search engines may choose to listen to it or ignore it as they see fit.

I apologize if any of that seems confusing. Here's a link to the SeoMoz guide on canonicals: http://www.seomoz.org/learn-seo/canonicalization and a blog post on the subject: http://www.seomoz.org/blog/canonical-url-tag-the-most-important-advancement-in-seo-practices-since-sitemaps

Have you looked into Mobile Responsive Themes for the WordPress site? That may be a better fit than a plugin.

It relies highly on all of the other pages which show up for the specific query, how well optimized they are, their relevancy compared to your page(s) and their continued efforts to rank for that query. I.E. Results May Vary.

Social Bookmarking sites are still useful... they just don't count for as much as they used to. Most of the ones you mentioned are fairly well known and well established sites so i wouldn't worry about getting any sort of penalty off of them (just don't expect them to magically skyrocket your rankings). Social Bookmarking can still be a good way to get some of your links out there and increase traffic. Just don't go overboard with it and don't go posting to really sketchy sites. I would have to assume there is more to their social and linking strategy beyond just those bookmarking sites though. If you use StumbleUpon, make sure that all of your links are adequately tagged because their auto-tagging algorithm has been known to be completely off base. I recently had a photo of gaming dice get flagged as "Sex Industry" by SU's algorithm because I didn't tag it myself.

From the Alexa website:

Alexa Traffic Ranks are based on the traffic data provided by users in Alexa’s global toolbar panel over a rolling 3 month period. A site’s ranking is based on a combined measure of Reach and Pageviews. Reach is determined by the number of unique Alexa users who visit a site on a given day. Pageviews are the total number of Alexa user URL requests for a site. However, multiple requests for the same URL on the same day by the same user are counted as a single Pageview. The site with the highest combination of users (Reach) and Pageviews is ranked #1.

So, If you want a better Alexa ranking then you need to increase qualified traffic to your website and entice people to view more pages.

There is no magic number of times that a keyword should be included in meta tags or copy. Their placement just needs to look and sound natural.

Your title tag on the homepage looks far less spammy now than it had before. Your meta-description is still a bit long so it'll wind up truncated in search results but it sounds much more natural than it did before.

Newer Google algorithms have come out, been tweaked and been refreshed repeatedly that almost exclusively target thin and spammy content. Something that may have worked in prior years won't work anymore. Perhaps you were hit with an algorithmic penalty during a refresh.

Can't believe I didn't think to post that link... ::facepalm::
That would've made sense for me to do earlier in explaining what some of the issues were on the site.

No, I can't give you new titles and descriptions for your pages. Do you have an in-house SEO and/or a copy writer on staff?

What hosting solution are you using? The free solution offered by Wordpress doesn't give you access to plugins or altering the html.

Every page title should be under 70 characters and unique from each other. The one on your homepage looks really bad... CSCS | CSCS Card | CSCS Test | Apply for CSCS Card | Apply for CSCS Test ... It's too long, overuses your target terms, and isn't exactly descriptive of the page. Your meta description on your homepage is similarly bad... Call 0207 199 9800 for Apply CSCS, CSCS Card, CSCS Test through Construction Helpline. Take the CSCS test, earn your CSCS card easily with Construction Helpline, Apply for your CSCS Card online. There is no good reason to say "CSCS" six times like that, its should be less than 160 character long (yours is 194) and should be relevant to the page. And your meta keywords tag is a red flag that you're trying to game the search engines to rank for CSCS cards... CSCS, Construction Skills, CSCS Cards, CSCS Card, CSCS test, CSCS tests, CSCS certificate, CSCS Health and Safety test, health and safety test, construction helpline London ... which will likely all lead to you being penalized in some fashion by Google.