Altering a background-image gradient and background color so they look the same across browsers

I have designed a gradient in photoshop CS2 that acts as the background-image and is placed at the top of the web page. The background color is suppose to be the same as the bottom of the background image so that it gives the appearance of a continuous non-broken page background. My problem is this effect is not consistent across the following browsers: Firefox, google chrome, safari, opera, navigator, and Internet explorer 6, 7, and 8. Across different browsers, i am getting alterations in the background image color and background color. which is resulting in the appearance of a non-continuous background.