code igniter view problem...

[eluser]Unknown[/eluser]
hi!
i am developing an application. i have two views a signin view and a home page and two controllers home and signin and also two models respectively for data fetching.
when the user opens the site, he will be presented a login page just like facebook, he provides username and password, and then he will be on his home page where he can upload photos, videos, posts, comments etc , a number of options.
the problem is that when the user logged in, how to call a respective view against an event such as sharing new post, this is done but then css is not loading even with base_url() call what to do??
plz tell me some trick
or if you have a small application developed in codeigniter plz i want to use that for my learning.
thanks in advance