Google PageSpeed Insights
As per Google’s definition: “These rules are general front-end best practices you can apply at any stage of web development”. In this sense, the score that you get from Google’s PageSpeed test does not tell you how fast your site actually loads, but how your site fares based on Web Optimization rules that advances the rendering and execution of front end codes (HTML, CSS, etc).
However, many of these rules are rather outdated for modern websites. If you ran the test against major websites like: http://www.facebook.com, http://www.microsoft.com, http://www.yahoo.com, you will get equally low scores.
Perhaps the only useful recommendation is the Optimize Image section. These are usually the major cause of slow websites. Please make sure to compress your images before uploading. Check out these image compression services and see what works for you:
Tiny PNG: https://tinypng.com/
Smush.it : http://www.imgopt.com/
Photoshop and/or other photo editing software
Full compliance to W3C is not a strict requirement to make your website SEO compliant. W3C compliance simply implies that the HTML and CSS codes that your website is built is compliant with the standards set by the W3C.
If you want your site to rank high in SEO, make sure that your site is regularly updated and has good quality and relevant content.
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