Can I improve my jquery dialog code, critisicm welcome
In JavaScript it is custom to give functions names that start with a lowercase letter so that they are not confused with objects.
Personally I'd avoid "hardcoding" the connection of the id of the link with the id of the dialog. (login -> login_dialog). Instead you could use the href of the link to refer to dialog. Example: 

&lt;a href="#login_dialog" class="dialog"&gt;login&lt;/a&gt;

var dialog = $(this.href.replace(/.*(?=#[^\s]*$)/, ''));


(The replace is necessary due to bugs in IE &lt; 8)


You are repeatedly assigning the click and resize event handler on each click, so that each time a dialog is shown a additional handler is added, but never removed.


(There is more, however I don't have time right now. Maybe I'll come back later)