Internet Explorer - CSS style is applied only after refresh

I'm quite new in web development. I encoutered a problem which is present only in the Internet Explorer - the CSS style of Main Menu is applied after refresh(just F5, not CTRL-F5). I used MVC .NET to make backend of site. I have no idea how to solve this problem.

The web site with this problem is:

http://ift.tt/23kfj9K

Thank you in advance.