Think about the last time you uploaded an image to your website. Chances are you downloaded it from a stock photography site, uploaded it to the backend of your site, and then inserted it to the page. This makes a shining example of image optimization, right? Not quite.
You’ve added a giant bowling ball weight to your site that’s slowing down the page speed. And, search engines can’t read your images without alt text.
http://searchenginejournal.com/on-page-seo/image-optimization/#close/
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