In case you missed it, Google announced back in February that they plan to release a major algorithm update on Tuesday, April 21st. According to Google, the update will expand their use of mobile friendliness as a ranking signal and will be the most significant update they’ve ever released. To put things into perspective, Google Webmaster Trends analyst Zineb Ait Bahajji was quoted at SMX Munich, saying that the upcoming update would be a bigger upset than Panda and Penguin.