Need to change look of drop down buttons

Hii!
We need to change the look of the drop down buttons on our top navigation bar to look something like this website's drop down menu. http://www.ringcentral.com/
Here is an example of our current top navigation bar and drop down menus.
http://www.topsecurityinc.com/testpage11.html
Here is the CSS that controls it.
ul.dropdown{position:relative;}
ul.dropdown li{width:159px;height:42px;text-align:center;font-weight:700;float:left;background:url(../web/images/global_bar_bk_r1_c2.gif) repeat-x 50% top;}
ul.dropdown a:active{color:orange;}
ul.dropdown li a{padding-top:12px;height:30px;text-align:center;display:block;border-right:1px solid #333;font:bold 14px verdana, sans-serif;color:#FFF;}
ul.dropdown li:last-child a{border-right:none;}
ul.dropdown li.hover,ul.dropdown li:hover{color:#000;position:relative;}
ul.dropdown ul{z-index:600;visibility:hidden;position:absolute;top:100%;left:0;}
ul.dropdown ul li{width:159px;font-weight:400;background:url(../web/images/global_bar_bk_r1_c2.gif) repeat-x 50% top;color:#000;border-right:1px solid #333;float:none;}
ul.dropdown ul li a{border-right:none;width:100%;display:inline-block;padding-top:4px;}
ul.dropdown ul ul{left:100%;top:0;}
ul.dropdown li:hover > ul{visibility:visible;}

Would also appreciate any help on adding the down arrows on the top buttons with drop down items.
Any specific code modifications would be greatly appreciated.