To add an answer to Jonathans, jQuery has its own documentation regarding $ (document) .ready:
" JavaScript , , , , . script , DOM . , .ready(), DOM , , , jQuery. , CSS , .
: http://api.jquery.com/ready/
EDIT:
, javascript, script, . :
1) script , , load().
2) , "" , , , script. , jQuery ( ), ( http://plugins.jquery.com/taxonomy/term/1939).