HELP PLS!!!! I NEED HELP W/ AN INTRO ANIMATION!

I've been trying numerous different css codes to add a kind of fading out intro animation to my page, but all is does is make the screen just a little darker before it fades to its normal colors. I've made a new account and tried it out with nothing else in my layout, and it worked. It might just be the current layout template that I'm using, but I'm not sure. Has anyone else had this kind of problem?