about: →show version info
about:version → same to about:
about:cache → show cache content
about:plugins → show info of plugins installed
about:memory →show memory usage
about:crash → crash the tab
about:dns → show dns info, like time
about:network → network tools
about:stats → shh! this page is secret!
about:internets → the tubes are clogged!
about:histograms →histograms resume