Drop down size problem in IE

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I have created dropdownlist using select with css. for me this is working fine in firefox& chrome.

but in IE overlapping on my dropdoemlist box.dropdown values are display on dropdown box.i mean hiding the drop down box. i want that shoud be shown under or upper of dropdown list box. this is working fine in firebox&chrome.IE only i am getting this problem...

<select name="ddlCountry" id="ddlCountry" ></select>

css:

.checkOutCont .shippingplicy select 
{ 
    width: 210px;
    font-size: 12px; 
    margin: 3px;
    padding: 4px;
    height: 29px; 
    padding: 6px 10px;
    margin: 0 0 10px 0; 
}