drop shadows for page elements

I am trying to put drop shadows on page elements like my Revolution Slider plugin using css.
http://www.abc-communications.com/?page_id=51

the css code I have tried:

tp-bgimg defaultimg {-webkit-box-shadow: 3px 3px 3px #7C7C7C;
    box-shadow: 3px 3px 3px #7C7C7C;
}

wpb_wrapper{
-webkit-box-shadow: 3px 3px 3px #7C7C7C;
    box-shadow: 3px 3px 3px #7C7C7C;
}

note: this code worked for all images other than the ones in the slider when used like this:

img{-webkit-box-shadow: 3px 3px 3px #7C7C7C;
    box-shadow: 3px 3px 3px #7C7C7C;
}

I guess i’m using the wrong css class but I can’t seem to find the right class name in chrome development tools.