Hi.
In which template can I change "EDIT" button's html? I tried in postbit_edit, but it didn't make any changes on my forums.
Yes, to edit the HTML you've to edit postbit_edit template. Make sure you are editing template of your current theme.
I'm sure... But I think there is problem with cache or sth like that.
I can see changes only in Opera... In FireFox it's still old button.
Its your cache issue, delete cookies and clear your browser's cache.
Revert the template to its default state, then edit it, then post your edited code in here.