Create new layer over that one, fill it with black and set opacity to 5 ~10% (totally up to you, but you should use the same opacity for all other buttons
Good idea diwave thanks but, i wanted to use border-bottom rather than box shadow. But will give that a go, goodonya maybe your solution is far more elegant, i have a feeling it is lol.
By border-bottom you know css code where we display three #colors to define border for bottom
Of course you will use colors in your CSS, not photoshop images. I mentioned above solution for “picking the right shades” of original color which means you will have to use Colorpicker in Photoshop to pick shade color.
Having it done in CSS automatically with border is not possible. Maybe with LESS (I never used that) or php coded CSS file. For that, you may want to check this out.