$('#my_id').before('<b>Hello</b>'); $('#my_id').after('<b>Hello</b>');There are also insertBefore() and insertAfter() methods but they work in a way I found counter-intuitive. The wrap() method is useful in some cases. If you want to replace the HTML in a tag use html() like this:
$('#my_id').html('<b>Hello</b>');More info: http://docs.jquery.com/Manipulation