Access 2010
Windows 7

Report --> Format TAB --> Width = 12.3042"

I can increase the width of a report with a mouse, but I cannot decrease the width with a mouse.
The width stayed locked at 12.3042" and cannot be made smaller.

The obvious thing to look for is is an object on the report whose right edge is stopping you making the page narrower.
Use Select All to highlight the difficult-to-see objects.

This may mean that there are one or more controls that extend past the width you are trying to make the report.

Might there be a Field or some kind of text box the width of 12.3042" or a text box entered in that area that is preventing you from making the width any less?

EDIT: I guess three heads are better than one!!!

Thank you all for your help. It was a couple of thin line that is 12.3042" long and it is way at the bottom of a report
that had prevented me from decreasing the size of the report.

Only if they are OUR heads, RAZ!:)