Can't change Body font family and size
 

Hi. I have a problem with my main CSS. I use vbulletin 3.8.2 and somehow can't change the font family and size of my forum names. I change BODY in the main CSS but in my forum nothing changes. Actually some parts like Font color , Normal links CSS font colors etc changes but when i edit Font Style Font Size ,Font Family no change occurs in my main page. What is wrong?
My board is www.students.kg