Exorting and Snapping problem with an axis.

Hey all, I’m still learn how to use blender and all. I’m using the wiki guide and decided to try to make a very simple person with maybe some definable features as a start. I start a new model, but when i go to extrude the cube and snap it the axis that is slides on is diagonal, and i must constany press shift y to make the axis straight. I’ve messed around with the functions but can’t seem to find the problem? Any clues?