System

Ctrl + H - help
Ctrl + O - upload file
Ctrl + R - clear
Ctrl + Enter - run
Ctrl + 1 - focus to HTML editor
Ctrl + 2 - focus to CSS editor
F11 - toggle fullscreen
Esc - fullscreen disable

Share

Ctrl + B - beautifier
Ctrl + F - find in editor
Ctrl + H - help
Ctrl + K - fold
Ctrl + / - toggle comment
Ctrl + Space - code complete

HTML

Ctrl + J - to matching tag

JS

Ctrl + I - show type
Alt + . - jump to definition
Alt + , - jump to back