twentytwelve theme custom menu not working

Hi Could you tell me if the twentytwelve menu uses java, as i created a child theme, to the child theme css I did not @import the parent css, as i would like to make the theme mobile friendly and with the parent css imported something seems to be overriding my media queiries. I am trying to create a 2 column dropdown and nothing is working plus i cant get rid of the assistive text – my top menu is a list
the .sub-menu-columns overide in admin menu css styles seems to work
see here test site – its always changing as i am creating it…
I also have something odd “skip to content” link – what is that and how do i display:none
http://bunddesign.com/pdm/

css

/* Navigation Menu */

/* Assistive text
.assistive-text,
.site .screen-reader-text {
	display:none;
}
.main-navigation .assistive-text:focus {
	display:none;}*/

.menu-main_menu-container { position:relative; z-index:1000; font-size:12px; font-family: 'Lato', 400, sans-serif; display:block; }
.main-navigation { text-align: center;} /* margin-top is different in media queries */
.main-navigation ul.nav-menu, .main-navigation div.nav-menu > ul { border-bottom: 0; border-top: 0;
    	display: inline-block !important; text-align: center;}

.main-navigation ul.nav-menu,.main-navigation div.nav-menu > ul {
         border: 0 none;
         padding: 0 0 0 0;
        text-align: center;
		 font-size:11px;
   }
.main-navigation li a:hover {
color: #04c928;}
.main-navigation li a:focus {
outline: none;
}
/*nav menu font color and bold font (font-weight)*/
.main-navigation li a {
    border-bottom: 0 none;
    color: #FFFFFF;
    font-weight: bold;
	 font-size:12px;
    line-height: 3.69231;
    text-transform: uppercase;
    white-space: nowrap;
}
/*current page nav font color & bold font*/
.main-navigation .current-menu-item > a, .main-navigation .current-menu-ancestor > a, .main-navigation .current_page_item 

> a, .main-navigation .current_page_ancestor > a {
    color: #04c928;
    font-weight: bold;
}
/*background color of sub-menu (dropdown)*/
.main-navigation li ul li a {
  background:#5e5f60;
  /*border-bottom: 1px solid #EDEDED;
  border-left:  1px solid #EDEDED;
  border-right:  1px solid #EDEDED;*/
  display: inline-block;
  line-height: 1.18182;
  padding: 0.571429rem 0.714286rem;
  white-space: normal;
  width: 11rem;
  z-index: 3;
  font-size:12px;
  text-align:left;
  border:none;
}
/*background & font color of sub0menu with mouse hover*/
.main-navigation li ul li a:hover {
        background: #595959;
        color: #04c928;
    }
.main-navigation li li {
  margin-left: -1em;
}
.main-navigation li.has-children > a:after {
 color: #fff;
 content: ' ▼';
 font-size: 10px;
 vertical-align: 1px;
}
.main-navigation li li.has-children > a:after {
 color: #222;
 content: ' ►';}
.sub-menu selector { width: 410px;}
.sub-menu-columns ul.sub-menu li {
    display: inline-block;
    float: left;
    width: 200px;
}
.sub-menu-columns ul.sub-menu li:nth-child(odd) {
    float: left;
    margin-right: 10px;
}
.sub-menu-columns ul.sub-menu li:nth-child(even) {
    float: right;
}

Hope someone can advise me
thank you
melanie