css problem

[eluser]loca[/eluser]
my tree view of CI folder is same the following:
EX:

+css
+system
-application
+model
-view
blogview.php
-controller
blog.php

when I import(link) css in my view file(blogview.php) and set default controller in routes.php file $route['default_controller'] = "blog";
It works

But when I use url ...index.php/blog/. Controller blog load but css not link to it
anybody help me. Thanks!