SEO iframes and redirects

Hidden redirects
Do you know what's the difference between these two custom error not-found pages? (where to find them? hint: look in your .htaccess file)

ErrorDocument 404 http://your_website.com/error404.php

ErrorDocument 404 error404.php

It appears that the first line returns 302 Found header code and then redirects to your 404 page, which is a really bad thing from an SEO standpoint and gets penalized. The second line gives you the normal 404 pages returning a proper 404 header code.

Too many 301 redirects
Can you recognize this code?

RewriteRule (.*) http://www.newdomain.com/$1 [R=301,L] 

You may think that it is OK when you redirect your old to a new domain (in case of having Panda penalty applied) via 301 temporary header redirect. But what happens if the old domain already has some kind of penalty applied. Well, it automatically transfers to your new domain, because as you've might noticed 301 is actually a PERMANENT redirect and transfers all the weight from the previous domain. So go, check and fix those two cases and be really careful!

Usage of iframes between subdomains
On one website(~500pages) with over 300 pages indexed in Google, I've used an iframe linking to other sub-domain in order to display relevant content. When I removed the iframe almost immediately, in less than 24 hours my indexed results grew from 300 to 360.
But why?
I started searching on the forums and it appeared that Google penalty filter was triggered by such a huge usage of iframes (mistakenly taken as poisoning attack). Here is a short explanation from Matt Cutts on this:

"Essentially, our search algorithm saw a large area on the blog that was due to an IFRAME included from another site and that looked spammy to our automatic classifier."
link: http://groups.google.com/group/Google_Webmaster_Help-Indexing/browse_thread/thread/68692a9aefae425f

Solution:
Remove all the iframes that you have or replace them with ajax calls or just static HTML content.
Wait a few days and run: site:http://yourwebsite.com to see the difference in the results!

Good luck!

SEO keyword density, canonical, duplicate content

Above is a sample screenshot is taken from Google's Webmaster Tools Keywords report. You may ask why should we need it when we can use Firefox integrated Show keyword density function?
Well, one benefit is that this function shows specific keyword significance across your pages. Let me explain what do this means:

Suppose that you are optimizing content for the keyword 'cars'. It's a normal practice to repeat 'cars' 2-3 times, style it in bold, etc... Everything's good as long as you do it naturally. The moment you overstuff your page with this keyword it will get penalized and lose its current ranking in Google SERPS. So you have to be careful with such repetitions.
Moreover in the report, you can see the overall website keyword significance. And because Google likes thematic websites it is really important for these keywords to reflect your website purpose or theme. Otherwise, you're just targeting the wrong visitors and shouldn't be puzzled by the high abandonment rate.

But, enough with the theory now let's discuss how you can fix some things up:

Check every individual webpage keyword density online via Webconfs and correct(reduce) words, that are being used over 2%. Again this % depends on your local keyword concurrency. So tolerable levels can vary up and down.

Add the 'canonical' tag to all your website pages:

< link rel="canonical" href="http://www.example.com/your_preferred_webpage_url.html" />

(and make sure to specify the URL that you really prefer!). This will reveal to the search engine what your legitimate webpage is. More info: http://googlewebmastercentral.blogspot.com/2009/02/specify-your-canonical.html

---

Blogger users can achieve adding canonical with the following code at the head section in the Template:

<b:if cond='data:blog.pageType == "item"'>
<link expr:href='data:blog.url' rel='canonical'/>
</b:if>

(it will remove the parameters appended at the end of the URL such as http://nevyan.blogspot.com/2016/12/test.html?showComment=1242753180000
and specify the original authority page: http://nevyan.blogspot.com/2016/12/test.html )

Next to prevent duplicate references of your archive( i.e .../2009_01_01_archive.html) and label pages( i.e. /search/label/...) from getting indexed just add:

<b:if cond='data:blog.pageType == "archive"'>
<meta content='noindex,follow' name='robots'/>
</b:if>
<b:if cond='data:blog.pageType == "index"'>
<b:if cond='data:blog.url != data:blog.homepageUrl'>
<meta content='noindex,follow' name='robots'/>
</b:if>
</b:if>

To prevent indexing of mobile (duplicates) of the original pages:
    <b:if cond="data:blog.isMobile">
<meta content='noindex,nofollow' name='robots'/>
</b:if>

And working solution blocking even the /search/tags from indexing, allowing only homepage and posts to be indexed:
    <b:if cond="data:blog.pageType == "index" and data:blog.url != data:blog.homepageUrl">
<meta content='noindex,follow' name='robots'/>
</b:if>