When I create a new file in AI CS 6, the artboard is larger than requested size, which shows up as a box within the too-big artboard. For example, when I create a new file, I set the artboard size menu to 1200 pixels wide by 750 pixels high, but the artboard created is about 6,000 pixels high and wide, with a black outline of the 1200 x 750 artboard that I tried to create. See attached screenshot. The actual artboard is much larger than the white area; I just cropped most of it in my photo software to show it here. What setting in the preferences or other menus fixes this problem? I didn't have it until today, so something got set incorrectly somewhere. I usually just see the 1200 x 750 white artboard against the dark background. It also seems to be happening now when I simply open an existing file. The artboard has suddenly increased to an enormous size.
What units of measurement are you using?
Pixels are not units of measurement (a pixel is just a square of colour and can be any size, although Illie incorrectly assumes that the width of a pixel is 1 Pica point).
Set your artboard size in inches, points, centimeters, millimeters, whatever you like but not pixels.
There are two basic document set ups. web and print. Web documents use the full artboard/pasteboard and simply create guides for the area you indicated.
If you want an artboard to match your desired size and are creating files for screen/web, choose "Basic RGB" for the document when creating a new document.
Pixels is an option in the new document settings, but I changed it to points and I still got the huge artboard. Same for picas. I also have it set to Basic RGB. Still no luck. Maybe reinstall AI CS 6. Could be a corrupt script somewhere.
Color modes aside for a moment, I suspect the large white area around your artboard is in fact the pasteboard, white in color because you've somehow lost or inadvertently mis-set your User Interface darkness setting.
Its not the pasteboard, because I can scroll to the top of the huge artboard and see the pasteboard which is set to gray. I did set the Profile to Basic RGB and still have the problem. I then actually uninstalled AI CS6, and reinstalled it, and the problem is still there. Something in some other part of the computer that has to do with this program did not get deleted, so it was active when I reinstalled AI. The problem is ruining my projects because when I save them with that 6000 pixel artboard, it takes 30 seconds to save it, and of course, it is a huge file. I am dead in the water until I repair it. I can't even edit existing graphics files, because they open with the artwork on that huge artboard instead of the original 1200 x 750. If I can't resolve it, I will have to use Inkscape for new projects. Adobe? I need you in on this. No one can figure it out, and it's destroying my workflow. I probably need a script that deletes everything that the installation put into any directory on my computer and then reinstall it.
I found all kinds of AI CS6 files left over after the uninstall. They were on the C drive under users, and in several sub-directories. I deleted everything that had anything to do with AI CS6, and then re-installed CS6. All is OK now. Adobe - Uninstall means remove EVERYTHING that the program installed on the computer, not just the exe file. All the leftover garbage files prevent a proper reinstall. Some settings file somewhere in that leftover mess was creating the oversized artboard. Please revise the uninstall function to remove ALL of the files that the program installed.