The SERPs can experience substantial changes due to a variety of causes. A powerful website might post new material optimized for the desired keyword, which results in it outranking other sites and pushing them down the rankings. Algorithm updates are also a major factor behind fluctuating rankings; search engines like Google often modify their algorithms, which can lead to alterations in the ranking landscape. Minor tweaks to the Google algorithm occur more than 500 times a year, generally known as the «google dance».