dem_speed

I downloaded a mod pack from ShotGunRaids and now, everyime i try to load forge, when its initializing the game, it crashes saying, ERROR Game Crashed. The game crashed whilst initializing game Error: java.lang.NoClassDefFoundError: net/minecraft/client/gui/guiscreen. I'm not really that good with stuff so, yeah. Can someone help or is there a problem? I tried deleting and redownloading them but it doesn't work. I tried taking the mods out and putting them back in and it doesn't work. Someone told me to ask for help on here so I guess yeah.