Deleting everything outside of canvas

I occasionally run into this problem where I'll place a large image on a small canvas and start erasing the background, then if I move it, I see parts of the background outside of the canvas. Is there a quick and easy way to delete parts of the image that fall outside of the canvas? It seems so simple, but I can't figure it out.

Select the canvas and then use Image/Crop to cut anything that falls outside the canvas.

That option isn't available. This is after I've used the Resize Canvas option to manually resize the canvas of an image with a transparent background. Does that help?

TerranRich said:

That option isn't available. This is after I've used the Resize Canvas option to manually resize the canvas of an image with a transparent background. Does that help?

Sorry, I have no idea what you are asking. Perhaps you could post an example of an image which shows the problem.

I use http://www.pixentral.com/