What is OptiFine HD?
Optifine HD helps improve your game. Maybe you are experiencing lag and you are jumping all over. Have you tried everything so far; short render distance, closing everything except Minecraft? Yeah me too and nothing works as well as Optifine HD!
Optifine HD is a combination of the Opti-fog Mod and the Opti-Mine Mod to bring you the Optifine Mod. It really does work and helped me a lot. Some people claim it doesnt work but I think it depends on every person. Only way you can find out is by testing it out!
OptiFine HD C5 Ultra Download Link: http://www.9minecraft.net/optifine-hd/