Wordpress dropdown menu doesnt work in IE - wordpress

Question

Im developing a website for a customer in Wordpress. The website www.daanen-shipping.nl has a dropdown menu which is working fine in FF/ Chrome and Safari but not in IE. The customer is useing IE 9. Apparently this is a common problem for many people. Compatibility view doesn't seem to be the problem.
Im kinda new in CSS and Javascript so i have no idea where to begin. I did hours of research with nu results. Hopefully there is someone that can help me.
Menu CSS:
#menu {
position: absolute;
right: 100px;
top: 180px;
}
#menu ul li {
float: left;
text-transform: uppercase;
font-size: 13px;
margin: 0 0 0 20px;
position: relative;
display: inline-block;
padding: 0 0 10px 0;
}
#menu ul li a {
color: #fff;
padding: 4px 1px;
display: inline-block;
}
#menu ul li:hover a, #menu ul li.current-menu-item a, #menu ul li.current-menu-parent a {
text-decoration: none;
border-bottom: #fff 3px solid;
padding: 4px 1px;
display: inline-block;
}
#menu ul li:hover a {
margin-bottom: 5px;
}
#menu ul li.current-menu-item ul.sub-menu li a {
color: #7b7b7b;
}
#menu ul li ul.sub-menu li, #menu ul li ul.sub-menu li a {
margin: 0;
padding: 0;
}
#menu ul li ul.sub-menu {
display: none;
}
#menu ul li:hover ul.sub-menu {
position: absolute;
top: 30px;
left: 0px;
background: #EBEBEB;
border: #ddd 1px solid;
width: 200px;
padding: 5px 0 2px 0;
overflow: hidden;
-webkit-border-radius: 5px;
-moz-border-radius: 5px;
border-radius: 5px;
}
#menu ul li ul.sub-menu li {
width: 100%;
}
#menu ul li ul.sub-menu li a {
padding: 8px 15px;
text-decoration: none;
border: 0px;
color: #7b7b7b;
}
If there is something else i need to post to be more clear, please let me know and ill work on it.
Thanks in advance!
William.

Answer 1

hit f12 and make sure that the site is using IE 9 standards. If it's not switch to IE9 standards and see if that fixes it. If it does, you can add some code to your header that tells the browser 'if the user is using IE 8 use IE8 standards or, if the user is using IE 9, use IE 9 standards'. IE is 3 browsers in one (7,8, and 9) and it has a bad habit of switching to IE7 and quirks mode on some sites. Let me know if it works when you change to IE9 standards and, if it does, I'll see if I can dig up the code to add to force the standards.