Please help : CSS Changed as I change the Forum URL in Admin Panel

[ptbm]

Hi everyone. I never use the vbulletin before, this is my first experience and vBulletin is amazing . But now I'm having difficulties in modifying the css.

I have 2 questions :

1. I have modified the additional.css in my localhost. Then I upload it to the server. But my modifications are gone. When I open the additional.css, the file is empty. Why is it like that ?

2. I just knew that I have to set up the Forum URL in the admin panel to be the URL where my forum will be located. When I modified the css and layouts in my localhost, the setting was still "http://localhost/forum". Then I uploaded it. All the links were directing to localhost. So I changed the forum URL to be the real URL where the forum is located. But my settings are gone. Only if I set the forum URL to be "http://localhost/forum" (which is the same when I modified the CSS in my localhost), my modification is working. Why is it that way ?

Please help, since I dont want to repeat the modifications again. Thanks so much for the feedback