title: CSS z-index issue top menu background
body: <p>I try to display a cloud as background on my menu, it actually gets displayed (just a little part) but it's hidden by the menu background. I had applied z-index on both items but it's not working.</p>
  
  <p>The CSS code I'm using is : </p>
  
  <pre><code>    /*** ESSENTIAL STYLES ***/
  .sf-contener {
  clear: both;
  }
  .sf-right {
    margin-right: 14px;
    float: right;
    width: 7px;
  }
  .sf-menu, .sf-menu * {
  margin: 0;
  padding: 0px 0px 0px 0px;
  list-style: none;
  }
  .sf-menu {
  margin: 10px 0;
  padding:0px 0px 0px 0px;
  width:980px;/* 980 */
  background: #383838;
  }
  .sf-menu ul {
  position: absolute;
  top: -999em;
  width: 10em; /* left offset of submenus need to match (see below) */
  }
  .sf-menu ul li {
  width: 100%;
  }
  .sf-menu li:hover {
  visibility: inherit; /* fixes IE7 'sticky bug' */
  }
  .sf-menu li {
  float: left;
  position: relative;
  top: 0;
  /*border-right: 1px solid #777;*/
  }
  .sf-menu a {
  display: block;
  position: relative;
  color:#fff;
  }
  .sf-menu li:hover ul,
  .sf-menu li.sfHover ul {
  left: 0;
  /*padding: 0px 0px 0px 0px;
  margin: 0px 0px 0px 0px;*/
  top: 35px; /* match top ul list item height */
  z-index: 99;
  width:auto;
  }
  ul.sf-menu li:hover li ul,
  ul.sf-menu li.sfHover li ul {
  top: -999em;
  }
  ul.sf-menu li li:hover ul,
  ul.sf-menu li li.sfHover ul {
  left: 200px; /* match ul width */
  top: 0;
  }
  ul.sf-menu li li:hover li ul,
  ul.sf-menu li li.sfHover li ul {
  top: -999em;
  }
  ul.sf-menu li li li:hover ul,
  ul.sf-menu li li li.sfHover ul {
  left: 200px; /* match ul width */
  top: 0;
  }
  
  
  /*** DEMO SKIN ***/
  .cat-title {
  display: none;
  }
  .sf-menu {
  float: left;
  margin-bottom: -2em;
  width: 100%;
  height: 75px;
  background: url('http://www.fdsfs.com/themes/fdfds/img/cabecera.png') repeat left center; 
  z-index: 100;
  position:relative;
  }
  .sf-menu a {
    position: relative;
    top: 20px;
    display:block;
      margin-right:2px;
      padding: 0 22px 0 20px;
      line-height:35px;   
      border: 10;
      text-decoration:none; 
      text-transform: uppercase;
      font-family:Handlee;
      font-size: 18px;
      font-weight: bold;
  }
  .sf-menu a, .sf-menu a:visited  { /* visited pseudo selector so IE6 applies text colour*/
  color: #916e6e;
  white-space:nowrap;
  }
  .sf-menu li ul {
    border:1px solid #f1b6b1; box-shadow:2px 2px 4px rgba(0,0,0,0.25);
    width:500px;
    padding: 0;
    margin: 23px 0px 0px 0px;
    top:0;
    background: white;
  }
  .sf-menu li li {
  background: white; 
    position: relative;
    top: 0;
    height:35px; 
    line-height:35px; 
    padding: 0;
    margin: 0px 0px 0px 0px;
  
  }
  .sf-menu li li a {
  font-size: 16px;
  text-transform: capitalize;
  top:0;  
  }
  .sf-menu li li li {
  background: blue;
  }
  .sf-menu a:focus, .sf-menu a:hover, .sf-menu a:active {
     font-weight: bold; 
     color: white;
     background: url('http://www.fds.com/themes/fdsfs/img/boton-b.png') no-repeat center -18px; 
     z-index: 90;
     position:relative;
  }
  .sf-menu ul li:hover, .sf-menu ul li.sfHover,
  .sf-menu ul li a:focus, .sf-menu ul li a:hover, .sf-menu ul li a:active {
  background: #eecfd0; //#4e4e4e; 
  outline: 0;
  } 
  /*** arrows **/
  .sf-menu a.sf-with-ul {
  padding-right:  2.25em;
  min-width: 1px; /* trigger IE7 hasLayout so spans position accurately */
  }
  .sf-sub-indicator {
  position: absolute;
  display: block;
  right: 10px;
  top: 1.05em; /* IE6 only */
  width: 10px;
  height: 35px;
  text-indent:  -999em;
  overflow: hidden;
  background: url('../img/arrows-ffffff.png') no-repeat -10px -100px; /* 8-bit indexed alpha png. IE6 gets solid image only */
  }
  a &gt; .sf-sub-indicator {  /* give all except IE6 the correct values */
  top: 11px;
  background-position: 0 -100px; /* use translucent arrow for modern browsers*/
  }
  /* apply hovers to modern browsers */
  a:focus &gt; .sf-sub-indicator,
  a:hover &gt; .sf-sub-indicator,
  a:active &gt; .sf-sub-indicator,
  li:hover &gt; a &gt; .sf-sub-indicator,
  li.sfHover &gt; a &gt; .sf-sub-indicator {
  background-position: -10px -100px; /* arrow hovers for modern browsers*/
  }
  
  
  /* point right for anchors in subs */
  .sf-menu ul .sf-sub-indicator { background-position:  -10px 0; }
  .sf-menu ul a &gt; .sf-sub-indicator { background-position:  0 0; }
  /* apply hovers to modern browsers */
  .sf-menu ul a:focus &gt; .sf-sub-indicator,
  .sf-menu ul a:hover &gt; .sf-sub-indicator,
  .sf-menu ul a:active &gt; .sf-sub-indicator,
  .sf-menu ul li:hover &gt; a &gt; .sf-sub-indicator,
  .sf-menu ul li.sfHover &gt; a &gt; .sf-sub-indicator {
  background-position: -10px 0; /* arrow hovers for modern browsers*/
  }
  
  
  /*** shadows for all but IE6 ***/
  .sf-shadow ul {
  background: url('../img/shadow.png') no-repeat bottom right;
  padding: 0 8px 9px 0;
  -moz-border-bottom-left-radius: 17px;
  -moz-border-top-right-radius: 17px;
  -webkit-border-top-right-radius: 17px;
  -webkit-border-bottom-left-radius: 17px;
  }
  .sf-shadow ul.sf-shadow-off {
  background: transparent;
  }
  li.sf-search {
    background: inherit;
    float: right;
    line-height: 25px;
    background:transparent;
  }
  li.sf-search input {
    -moz-border-radius: 0 5px 5px 0;
    padding: 5px 0;
    position: relative;
    top: 1px;
    padding-left: 30px;
    margin: 18px 6px 0 0;
    background: #fff url('../../../../img/search-zoom3.png') no-repeat left center;
    border:1px solid #777;
  }
  
  
  /* hack IE7 */
  .sf-menu a, .sf-menu a:visited {height:34px !IE;}
  .sf-menu li li {
  width:200px;
  background:#726f72 !IE;
  }
  
  #block_top_menu .category-thumbnail {
    display:none;
    clear: both;
    width: 100%;
    float: none; }
    #block_top_menu .category-thumbnail div {
      float: left;
      width: 33.33333%; }
      #block_top_menu .category-thumbnail div img {
        max-width: 100%; }
  #block_top_menu li.category-thumbnail {
    padding-right: 0; }
  </code></pre>
  
  <p>Any ideas? </p>
  
  <p>Thanks for your help</p>