When Per User Display Screen Resolutions is different, I think Oracle Form 10g R2 can't support "Auto" that Function.
In my opinion:
You should ask every system user to set "SAME" Display Screen Resolutions(ex: 1024p * 768p etc...) in the Monitor.
then you can set Windows Property Physical Width/Height.
thanks you so much.
my problem is solved by changing width = 100%, height = 100% in formsweb.cfg file.