I installed a Minecraft mod and now Minecraft Won't open

I installed a Minecraft mod and now Minecraft Won't open. Help?

Added (1). I installed Mo' Creatures for minecraft 1.7.2 and now when I open the launcher, everything happens as its supposed to. But when the browser goes away… Nothing happens. Please Help:/

Added (2). *Launcher not browser*

Try uninstalling the mod. Just find your ".mincraft" folder, and delete minecraft.jar. You might've either installed it wrong or downloaded a misleading or false file. With my experience that can happen frequently.

1. Download mod
2. Application support>minecraft>mods and drag mod to mods folder
3. Download minecraft forge get the version that the mod is
4. Activate forge by clicken it
5. Open minecraft and click edit profile and change to forge version