how can I line-up selected/all verticles for example in x-axis?
I don’t really understand the question but maybe: select the verts then scale them to 0 on the other 2 axis?
I try to describe the problem.
I am making my home.
in that image,that red one is going to be face of wall that is outside. I made that by taking faces from that side rooms and joined verticles. I tried to move verticles in same level so that wall would be flat.
in second picture you can see few faces that are different shade because they are different position in Y-axel. I would like to know is there way to select all verticles and set same Y value for each of them
What you want is scale on one axis.
To do that select all the vertices on the wall (with B, or use L to select the connected vertices). Then press s (scale) then x (or y or z) then keep CTRL pressed (so you scale with 0.1 increments) and move mouse until you scaled all the vertices in the same plane.
Also try remove doubles on your wall.
Select all the verices and then do a scale to 0 on the Y-axis (constrain to the specific axis with MMB)
You can also do the following key combination:
Make sure you are scaling to the center of the selection and not the cursor.