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Sub domains have pros and cons. If you expect displaying multiple pages of your domains (main and sub) on the search result pages for the same keyword then sub domain will be better option but sub domain pages won't get more value from PR of main domain.

I would recommend to update pages as soon as you complete each change. Since no one knows about the accurate Google process time for each change, no need to connect your changes.

First you need to check if multiple URLs displayed under each title are working and rendering different pages.

Sometimes redirect may have syntax issues. Post your result to discuss other options.

I would suggest to use "noindex" for completely dropping the unwanted URLs from the index of search engines.

Check Google guidelines at: http://support.google.com/webmasters/bin/answer.py?hl=en&answer=93708

Aggressive approach would be reporting domains with non relevant links to Google.

As long as the article is more interactive, I don't see any problem. Most linked vs. more valued links will be an another discussion point.

Articles of the other types like the following also can be explored:

1. DIY - do it yourself

2. Creative ideas - e.g., Creative Christmas makeovers

I would suggest to start from competitive link analysis.

Try to understand how your competitors are building links for each particular product line. This will help you to develop a link building strategy including article posting, developing company blog, social optimization, promotional campaigns, etc.

I would suggest you to fix this issue soon. Otherwise Google may report soft 404 error at one fine day.

Also check your redirect rules. Redirecting error pages to home page should be avoided.

Blog pages have more value than the knowledge section static pages. Also blog posts and knowledge section contents should have different tones. From user perspective, normal users will like to read blogs instead of knowledge section which used to attract serious users.

So blending both will be the right approach.

Important items to get images indexed:

1. Al text with the keywords

2. Image file name with the descriptive text

3. Image site map

For better user experience:

1. Good quality photos

2. Lossless compression

3. Declaring width and height

4. Surrounding text or caption

Search query report will be of great help to analyze organic CTR and ranking. Even though the data is available only for the last 35 days, the report is very valuable.

Surprised to hear that you got such question from designers.

Configure Google webmaster tools first.

http://www.google.com/webmasters/

Download all the errors and recommendations to forward to any programmer/designer.

There won't be any penalty if 404 pages are redirected to other pages. At the same time Google prefers to see 404 error for pages that are not available.

Couple of steps may reduce 404s:

1. Check on page / internal links if they are working URLs and update them with valid URLs

2. If you are linking your pages from different site, check the URLs used

3. If you are using free or paid directories, paid campaigns etc. check if the URLs are valid

Google may reduce the value for domain with keywords in near future.

Watch the following Matt Cutts video:

http://www.youtube.com/watch?v=rAWFv43qubI

If domains are available for your desired keywords, you may go for it. I wouldn't recommend to change keywords as well as additional investment.

It depends on the size of the site. As long as it is reasonable, would not worry too much about it.

Check this:

http://www.mattcutts.com/blog/how-many-links-per-page/

You need to check if the URL has correct image file name. User experience will be poor if they get such 404 error while accessing your on page elements.

Redirecting such 404 error page to other page is not a recommended practice. Search engines should get 404 error from incorrect URLs.

Don't see any press release or blog post from Google today to support your findings. If one or few sites moved that may be site specific and may need further deep analysis.

Checking historical link values is one of the options.