Google has just announced that as of April 21st they will be adding a Mobile-Friendly Ranking Factor into their algorithm. This is BIG NEWS for two reasons. Google is actually telling us WHAT will happen and WHEN it will happen. No 'read between the lines' type of algorithm update. Google has been warning webmasters for some time that this was coming. Now that mobile is much bigger part of the search world and in an effort to make mobile searches more relevant to users, Google is adding this factor into their algorithm. If you've been ignoring the call to make your site mobile-friendly, you may pay the price come April 21 with a drop in ranking!
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I believe you need to continually evaluate marketing results and be willing to change on the fly when results are clearly indicating that need. We all do an annual review at the end of our fiscal year. For many that is at the end of the calendar year.