walkcycle repetition help im a noob thats right have pity :(

yeah i have a stupid robot which i rigged.
i can make it walk by adding keys to every like 10 frames, but his feet sink into the floor, can you help?

also i want to make him keep on walking for some time without me having to animate him all the time. like repeat his walk cycle. how?

please reply quick.

http://mediawiki.blender.org/index.php/BSoD/Introduction_to_Character_Animation/2-second_animation