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The article addresses this.  Setting the language in the content-language meta tag will override the lang attribute in the html tag or the title tag.  They're recommending to use one method to set the language and stick with it, rather than setting the language in multiple places on a page.

So, setting the lang on the tag is fine, just don't set meta content-language tags that specific a content, or set the lang in your <title>tags.</p></title>

It's all about quality unique content.  The reason a lot of .edu's do well is because they have a lot of domain authority and a lot of them have been around for a long time.  The directories that pass good link juice have this going for them as well.  If you create a link farm on an .edu domain, you won't be fooling the search engines.  It'll be a brand new site with no links to it that has no unique content which links out to a bunch of sites which may also be spammy, aka a link farm.

I'm not sure what your goal is with this site.  If your goal in creating the site is to give an SEO bonus to these site you're linking to, I doubt it do any good.  If your goal is to create a site that is a directory that is useful to people, and people start using it, linking to it, sharing it, then it could work.  If your goal is to put up a site that has some links for your own enjoyment, go for it!  If Google thinks your site is a link farm, it's not like they're going to dispatch agents to your house in the middle of the night or anything.

I think switching the two versions should be fine.

You can set up rel alternate hreflang tags if the content on your site is duplicate between English and Spanish.  This will help the search engines understand that these are alternate pages based on the language, and help Spanish searches get the Spanish version of pages, and English searches get the English versions.  Google talks about that here.  You can do it on the page, or in your sitemap.

You can use the meta language tags or set the language in your HTTP headers for Bing to understand what's going on (see here).

Google. Pick a few sentences or phrases in the article, and Google them. If you put quotes around them, Google will only return results with exact phrase matches. If any of the phrases show results, look and see if the article is the same.

CSS positions things on the page, so if you remove it, it's not surprising that lots of elements overlap.  The page isn't going to look good.  This is nothing to worry about.

If you want to see how a page looks to search bots, view the source of the page, don't disable the CSS.

Take a look at this Whiteboard Friday; Cyrus can answer your question better than I can: http://www.seomoz.org/blog/beyond-exact-match-anchor-text-to-next-generation-link-signals-whiteboard-friday

I wouldn't do that. rel=canonical is supposed to point between truly or near-truly duplicate pages, usually when things like URL parameters are on URLs but don't do anything to the content.  These are completely different pages, category pages on your site, vs. ones on your blog.  I would not recommend it.  Chances are Google will just ignore your rel=canonical.  It would likely not do any damage to your rankings, but who knows down the line... you never know when they'll release a Google aardvark or some other animal from the Google zoo.

Note my work firewall blocked the blog URL so I was looking at a cached version on Google.  If the pages are truly duplicate (which they didn't appear to be), go for it.

If you have the check my links extension in Chrome, it makes it easy to find URLs that 404 on any page.  You can install it here: https://chrome.google.com/webstore/detail/ojkcdipcgfaekbeaelaapakgnjflfglf.

Assuming you've verified your site in Google Webmaster Tools, you can go in there and to go Crawl > Fetch as Googlebot.  Put that page, and have Googlebot fetch it.  Once it's done, you can click on the "Success" link, and this will show you exactly what Googlebot fetched with regards to that page.  Make sure the source code you're seeing here is what you expect.

You indeed have a duplicate content problem.  The PageRank for the www.telikin.com/index.php page is not contributing towards the PageRank for your www.telikin.com page.  You should 301 redirect www.telikin.com/index and www.telikin.com/index.php to www.telikin.com.  Personally, I don't know how to write the actual redirect, but make sure when you do it that your home page works as you could potentially create an infinite redirect when messing with your site's index page.

The trailing slashes don't matter, meaning Google knows www.telikin.com/index.php/ is the same page as www.telikin.com/index.php, so you don't have to concern yourself with that.

I'd recommend not changing these to 301 redirects.  301 redirects are permanent, meaning browsers can (and most will) cache them.  Suppose you switch to 301 redirects.  If one of your users' sessions ends, and visits subscribers.mywebsite.com/article1, and gets 301 redirected to www.mywebsite.com/article1.  They log in, and click the link to subscribers.mywebsite.com/article1.  If the browser has cached the redirect, they'll be taken back to www.mywebsite.com/article1!  You definitely don't want that to happen.

Some recent experiments have suggested that 302s do pass some link juice (here's one).  I'd look up how many links you're actually talking about here linking into subscribers.mywebsite.com.

Rather than doing redirects when users sign in, the best thing from my perspective would be to check to see if the user is signed in, and serve the all the content under the same URL.  So all the content would be under www.mywebsite.com, but if they're not logged in, they get the extract of the article, and if they're signed in, they get the full version.  That way all of your links would point to the correct page, subscriber or not (and then you could 301 all the subscribers.mywebsite.com links to www.mywebsite.com, since those URLs wouldn't be needed anymore).

Not that I'd recommend cloaking, but you could see if it's Googlebots IP address, and do 301 redirects in that case.

I don't see any problem with putting a noarchive on your page.  We do it on all of our skill pages, because those pages get their content via AJAX, and as such appear broken when viewing the cached versions.  Doing this should not have any effect on your rankings.

301 redirecting pages that are no longer used to another (hopefully) relevant page on your site is a very common tactic and is a best practice, so I wouldn't be worried about that either.

The wayback machine will still archive your content, and your competitors may look it up there.  If you want to keep your old pages out of their index, you'll need to disallow their crawler in your robots.txt, and keep it from visiting those pages, or your entire site.  There's info on that here.

Weird. We were having a problem where lots of our skill pages were getting our

<noscript>text used as page descriptions on Google SERPS.  We added these comments, and Googlebot reverted to using our meta description as the page descriptions in SERPs.  It could have been a freak coincidence that Google stopped using our <noscript> text right after we implemented the tags, or possibly Google was (possibly accidentally) supporting them for web search awhile back when we originally did this, and now has stopped supporting it.  Anyways, our SERPS remain clean of our <noscript> text today (<a href="https://www.google.com/search?q=site:www.ixl.com/math/grade-5" target="_blank">example</a>).</p> <p>John Mueller recently commented on that Quora thread saying it won't do anything for web search, so IMO that puts this to rest.</p></noscript>

The point I'm trying to make is that a CSS problem likely won't result in any huge changes in your SEO.  There's a CSS problem if you can visually see something positioned or sized incorrectly on your pages with CSS enabled, not disabled.

Search bots will do some CSS/Javascript rendering, but more towards seeing how large things are on the pages (& trying to find your headers), making sure you're not hiding text (setting text colors the same as background colors), and things of that nature.

It sounds like Martijn solved your problem, but I still wanted to add that robots.txt exclusions keep search bots from reading pages that are disallowed, but it does not stop those pages from being returned in search results.  When those pages do appear, a lot of times they'll have a page description along the lines of "A description of this page is not available due to this sites robots.txt".

If you want to ensure that pages are kept out of search engines results, you have to use the noindex meta tag on each page.