Internet meme popular on imageboards. The origin of this meme is actually from the game Starcraft. A screenshot of one game was sent in to SomethingAwful where one noob player said "dude, where are you?" and his Zerg-rushing opponent 1337h4x replied "im in ur base, killing ur d00dz". The humor of this sentence is that the noob had not realized his opponent was inside his base. Since then it has become one of the most popular internet memes and spawned more photos than you can shake a stick at.
im in ur fridge eating your f00dz
im in ur white howz creationizin werdz