Css doesn't apply to my pages.

[rockxuyenmandem]

I use Css to apply to my lable control and it work well in design mode: http://i2.photobucket.com/albums/y26/rockxuyenmandem/1-1.jpg However when i view this page in browser Css doesn't apply changes: http://i2.photobucket.com/albums/y26/rockxuyenmandem/2-3.jpg Could someone give me the reason, thanks so much:)