Check the Response Codes of Your Header and Act Accordingly

When a visitor loads your website, all sorts of various responses can load for them. To help diagnose HTTP Header problems, use this HTTP Header Response Tool & Code Key. You can discover what code loads for your website, then see what steps you need to take to fix it.

http://www.internetmarketingninjas.com/header-checker/

Flag Your No-Follow Outgoing Links

No-Follow links can be a powerful tool for your website, but they can be a harmful detriment if not handled properly. Use this No-Follow Finder to help discover the amount of no-follow links you have at a certain URL, then flag them to make sure you're taking the proper steps moving forward.
http://seotoolsforyou.com/tools/no-follow-finder/

Validate Your Website's Mobile Readiness

If you haven't given any thought to the mobile readiness of your website, you're missing out on a lot of revenue potential. People aren't just visiting pages on their phones, they're purchasing and more. With the W3C MobileOK Checker, you can find out if your website is ready for mobile phone users.

http://validator.w3.org/mobile/

Check your SEO

Great Tool to check your SEO: http://tutor.rs/

Site's SEO with this Free Microsoft Toolkit

 No, the toolkit doesn't just provide metrics and tips for increasing your site's influence in Bing. This Microsoft SEO Toolkit will help you increase website traffic and revenue, by increasing your influence with major search engines. There are tools to help you improve customer experience as well.

http://www.microsoft.com/web/seo/

Does Your Site Contain Enough of the Right Keywords?

Check to see if your site contains enough of the right keywords with the Keyword Density Checker - Keyword Cloud Tool. Type in a URL, and you will see a visual display of the keywords on that site along with a report of all the keywords used, their count and density.
http://www.webconfs.com/keyword-density-checker.php

Check Your SEO & Detect Problems

If you've just completed your website's design, or simply want to give your current site a double take, then try this On-Page Analysis Tool. It will allow you to analyze a wide variety of elements on your website - from SEO, to image, and external/internal links.

http://www.phpjabbers.com/seo-tool.php

Improve Your Site's Traffic with these Comprehensive Reports

Your website can always be improved upon. There should never be a point when you stop looking to improve different aspects of your site. Using URLTrends, you can improve everything from your site's SEO to more technical issues. You can also look at ways to improve your site's social media standing.

http://www.urltrends.com/

Optimize your website speed

With our high speeds of internet now, everyone deserves and wants a fast web experience. This tool from GTmetrix will test many aspects on your website load speed and give you a grade with details on problem areas! Check your website grade now!
http://gtmetrix.com/