I have a button in my theme that changes color on hover. I needed to change the hover color of the button and did so be creating a new png file in photoshop that matches the old file exactly (as far as I can tell) as the old file, except for the new color. However, when I use the new png file, the button appears to have a constant white border during hover or not.
This is the page. look at the "Login" and "Register" buttons in the top right corner.