/* Turn on a 16x16 scrollbar */
::-webkit-scrollbar {
    width: 16px;
    height: 16px;
}
 
/* Turn on single button up on top, and down on bottom */
::-webkit-scrollbar-button:start:decrement,
::-webkit-scrollbar-button:end:increment {
    display: block;
}
 
/* Turn off the down area up on top, and up area on bottom */
::-webkit-scrollbar-button:vertical:start:increment,
::-webkit-scrollbar-button:vertical:end:decrement {
    display: none;
}
 
/* Place The scroll down button at the bottom */
::-webkit-scrollbar-button:end:increment {
    background-image: url(images/scroll_cntrl_dwn.png);
}
 
/* Place The scroll up button at the up */
::-webkit-scrollbar-button:start:decrement {
    background-image: url(images/scroll_cntrl_up.png);
}
 
/* Top area above thumb and below up button */
::-webkit-scrollbar-track-piece:vertical:start {
    background-image: url(images/scroll_gutter_top.png), url(images/scroll_gutter_mid.png);
    background-repeat: no-repeat, repeat-y;
}
 
/* Bottom area below thumb and down button */
::-webkit-scrollbar-track-piece:vertical:end {
    background-image: url(images/scroll_gutter_btm.png), url(images/scroll_gutter_mid.png);
    background-repeat: no-repeat, repeat-y;
    background-position: bottom left, 0 0;
}
 
/* The thumb itself */
::-webkit-scrollbar-thumb:vertical {
    height: 56px;
    -webkit-border-image: url(images/scroll_thumb.png) 8 0 8 0 stretch stretch;
    border-width: 8 0 8 0;
}

http://almaer.com/blog/tag/scrollbars

Change the default scrollbar on webkit engines

css

CSS