Hello im a newbie in blender 2.66a version so my question… is it possible to extrude face downwards with mirror modifier x,y,z i want to preserve all only the face to go downwards now it goes in both directions up/down
A mirror modifier does exactly what it says, it mirrors the object on the set axis. In this case you would have to turn off the Z axis mirror if you want it to not be symmetrical on the z axis
im using this tutorial http://www.blendtuts.com/snowman and my problems start in first part at 27.38min the first one was to join vertices with j needed to join 4 it join 2 , second one was with mirror modifier i follow the tutorial strictly BUT … 
in the tutorial everything works fine but not in my case 
thanks in advance
in use a tutorial from http://www.blendtuts.com/snowman part 1 in this tutorial theres no problem at all …but in my case i do the same and its not working … ty
in advance for replys
You need to pay attention to the options in the mirror modifier panel. First you had all three axes checked off, then only the x axis. I haven’t watched the tutorial, but I suspect if the instructor is using the various axes to make this model, he is telling you when to change them. If not, it’s a poor tutorial. You should really give some more detail than just say, “its not working”. What, specifically, is your mesh not doing that you think it is supposed to do? People are not going to go through the tutorial just to find out what your problem is, you have to tell us.
If you push face downwards and it goes really far down increase a bit Merge Limit and move face back up until they ‘stick’. Use Shift key while increasing value.
Well guys sorry, but are you reading ??? the problem is with Z axe “ONLY DOWN” extrusion with mirror modifier in 1st snapshot is clear … it extrude in both directions i want only Z axe DOWN no UP try it out yourself eppo i cant extrude shit with mirror modifier >>> clipping option checked when is unchecked extrusion goes in both Z axes … only down needed thanks for reply’s