trying to make white background transparent

[gisdude]

Hi all. I am trying to make a white background in my tif file, transparent. I did this yesterday, but now the white has come back.
I select image -->right click --> choose transparency. then it asks for the "transparency mode" which I enter "ON". then it just closes out. there is no dialog box to ask me which color to choose.

This just worked yesterday.
Thanks

[bflorence]

Maybe you've already tried this.
In the "Properties" box you can select the color you want to be transparent.