Manual talk:$wgUseETag

What's an ETag header?
 * See en:HTTP ETag. i Alex  10:36, 27 July 2008 (UTC)

Description
By setting this to be "true" in your LocalSettings.php, intelligent web browsers are able to avoid re-downloading content and instead rely on cached content more reliably. This can improve the apparent performance of your wiki. --Gadlen 19:00, 12 October 2008 (UTC)