Photoshop: How can I fill the background in as TRANSPARENT instead of white?

I have a picture of mountains as a quick mask. The edges fade out to a white background. I need to change this background from white to transparent/clear. Does anyone know how to do this? Thanks!Photoshop: How can I fill the background in as TRANSPARENT instead of white?
BUT ONCE U SAVE THE CUTOUT AS A JPG it automatically fills in the white... try adobe's website and look under formats to save under, that might play a role.Photoshop: How can I fill the background in as TRANSPARENT instead of white?
you should be able to just select the white part and delete it. then you will have to save the image as a file type that supports transparency I'm pretty sure a GIF should work.