I know that some of the base units for mobile gridding are usually arbiters and Devourers, but I've occured several offset glitches using arbiters which seem to be more recommended then devourers, were devourers in an arbiters place would have glitched like no tommorow. So can anyone help me with this little problem, what units have a reduced chance of offsetting and second, other then making the unit stand still, how do I reduce the chance of an offset happening?

I believe what you are experiencing is the offset glitch, which is not specific to a particular type of unit, but rather the position of the mobile grid.

For your interest, the following air units work for a mobile grid:
- Arbiter
- Mutalisk
- Devourer
- Guardian

I ran a search for mobile grid topics for you which have several helpful answers regarding the offset glitch and how to fix it. Here are a couple topics:
http://www.staredit.net/topic/13591/ (see rockz's post)
http://www.staredit.net/topic/10370/

Hope this helps.

http://www.staredit.net/starcraft/Grid_Systems#The_Offset_Glitch

What I do to fix it, is wherever my mobile grid is happening, I create 3 devourers or whichever unit type, and they create an L shape. The one on the bottom right will be aligned correctly to the grid, so get rid of the first two, center a location on the bottom right devourer, then create 6 more devourers (for a total of 7 on the map). The 6th devourer created will be approximately over the original center of the mobile grid location, but he will be snapped to the grid because he was created off of a grid that was correctly aligned. So re-center your grid location on him, remove all the devourers, then you have an aligned location to work with and you can use whatever grid you like.

3 4 7
2 6 8
1 5 9

X
X 3

6 5
1 4
2 3 Huh?...
I can understand the L shape part, but not with more then 4. If you remove 2 and then create 6 for 7, wouldn't the location just center in on the 4th devourer which is above the middle one which is the 6th in the centering order?

Take a look at the image.
See how the top is above middle and there is a gap? the top devourer is correct. The middle devourer is not.

So, you center a location on the lower devourer (also incorrect), create a new grid (will be also incorrect) and it will look identical to the previous grid. However, now the "top" is correct. Center a location on the top devourer and you have a correct grid.

Units are detected in a location using the X coordinate. First it looks at the X. Leftmost units first. Ties go to the newest unit in that location (I think, it might be the unit with the lowest address). Thus, the actions would look something like this:

Create 2 devourer
Center location
remove 2 devourer
create 6 devourer
center location
remove 6 devourer
create grid.

Helpful. So wait an offset glitch is caused by grid units not spawning on the top?

If you create 1 unit, it will spawn at the center of the location, no matter where it is.
Other units do not do this, and are instead placed at the nearest 16x16 fine grid location where they will fit. This is why when you create zerglings, they stack so well (except the first zergling).

So I can use the partial devourers for any mobile grid to reduce offsets?

Yes.

Then that leads to another question. Air unit offsets, you can't stop those can you? So will this allow the grid to refix itself after a round, Alittle bit or will it still just offset like any other

To stop air unit offsets, you move the air unit away before you make the grid.

It's not exactly a perfect situation, so you'd do best to just not use air units at all. As far as refixing itself, it will only be fixed when there are no air units there.

I see now. I notice now that with the partial grid put into some of my mobile grids, if the grid messes up for a split second it seems to refix itself quite quickly instead of staying messed up for the duration its there.

I used the partial grid with a Devourer grid that spawns Guardians just before and it constantly offsets no matter what I do. Do guardians displace devourers even if they are removed only seconds after?

Any air unit will displace any other air unit. You must completely remove the Guardians before setting up the Devourer grid.

Thats what I mean. I remove the guardians before I do the next grid, and it messes up completely. Do Mobile grid types mess with eachother? Say after 1 set 3x3 grids, I do a 5x5

No. If there are no air units when you are making a mobile grid, then it should not cause a problem. If you're making two grids at the same time, it can cause a problem, though. Keep in mind that dying air units still exist for the length of their death animation.

So say I have one of the Devourers Killed within the middle of the grid instead of removed, will that mess the grid up?

Yes. The Devourer will still exist for the duration of its death, and can affect the mobile grid until the death animation is complete (I believe, not entirely sure on the details).

Wow. So I'l have to use another unit to even make it work.