This is the {{warning}} template.

This template should be used for important warnings about an article or a user that cannot be shown using a more specific template. Please only use it when something is seriously wrong and other people might not otherwise know about it.

{{Warning|Include warning here.}}
  • {{Warnsign}} – small, inline version for talk page threads
  • {{caution}} – for messages indicating serious problems
  • {{notice}} – for important comments
  • {{consensus}} – for topics based around reaching consensus
  • {{ambox}} – article message boxes of any type; there is comprehensive documentation of its different options
  • WP:Template messages/User talk namespace - Lists all kinds of warning templates to put on user talk pages.