503Most of you probably know what a 404 code is. SEO pros use 301 redirects as well. What is a 503 though? It’s a code telling the Google bot that a site is temporarily unavailable and not broken for good.​ You need it when performing site maintenance resulting in downtime.​ See:http://googlewebmastercentral.blogspot.com/2011/01/how-to-deal-with-planned-site-downtime.htmlA/B TestingThe process of comparing two (or more) versions of a page to find out the best performing one, i.e. the one that is ...