Drop down menu hidden (Fixed)

In this part of the of the CSS give the z-index a higher value e.g. 10

#primary-menu-wrapper  {
margin:0 auto;
position:relative;
width:960px;
z-index:5;
}

so it becomes

#primary-menu-wrapper  {
margin:0 auto;
position:relative;
width:960px;
z-index:10;
}

You need to disable CSS optimization and reload the page and apply it again or clear the cache at:
Administer > Site configuration > performance, to make the CSS changes work.

Hope this helps you further, please let me know.

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Changed issue title