Weird deformation of rigging and posing in blender

Question

I follow some online tutorials to do the rigging and posing in blender. I create bones and vertex groups, then bind them together. When I move on to rigging, the deformation of the mesh is quite weird. I searched on the internet and didn't find an answer. I wonder if anyone can help? Thank you very much!

Image here (http://s17.postimg.org/wn4z8fjd9/strange.png)

Answer 1

It looks like they have wrong weights for the bones. Try first to remove the parenting for the mesh and parent the mesh again using the "automatic weight" option. After that you fix the remaining problems in weight paint mode