When I view my site in IE everything looks good. When I view my site in FireFox there is a box that shows up when I rollover one of my menu options. I can't find anywhere in my CSS that would add a background box. Here is my CSS:

.RootMenu_Static TD{
 background: transparent;
 color: #fff;
 font: Verdana;
 font-size: 12px;
 font-weight: bold;
 margin: 0 auto;
 padding: 5px 0 0 15px;
}

/* the items in the main 'root' menu in their hoverd state - referenced in the xml skin file */
.RootMenu_Selected TD{
 background: transparent;/*url(bg_menu.jpg) repeat-x;*/
 color: #c00;
 font: Verdana;
 font-size: 12px;
 font-weight: bold;
 margin: 0 auto;
 padding: 5px 0 0 15px;
 
}

.RootMenu_Active TD{
 background: transparent;
 color: #fff;
 font: Verdana;
 font-size: 12px;
 font-weight: bold;
 margin: 0 auto;
 padding: 5px 0 0 15px;
}

.RootMenu_Breadcrumb TD{
 background: transparent;/*#D8E0EB; url(bg_menu.jpg) repeat-x;*/
 color: #fff;
 font: Verdana;
 font-size: 12px;
 font-weight: bold;
 margin: 0 0 0 0;
 padding: 5px 0 0 15px;
}

.HeaderPane { margin: 0; width:892px; height:34px; padding:0 0 0 0; vertical-align: top; background: transparent url(images/menu_bg.jpg)}
.LogoPane { margin: 0; width:892px; padding:0 0 0 0; vertical-align: top;}
.TopPane, .BottomPane, .ContentPane { margin: 0; padding: 10px 7px 7px 0; vertical-align: top; width: 100%; }
.LeftPane    { margin: 0; padding: 10px 35px 7px 25px; vertical-align: top; text-align: left; width: 25%; }
.RightPane    { margin: 0; padding: 10px 25px 7px 35px; vertical-align: top; text-align: left; width: 25%; }
.SidePane    { margin: 0; padding: 0 7px 7px 0; vertical-align: top; }
.MiddlePane    { margin: 0; padding: 0 7px 7px 0; vertical-align: top; width: 50%; }
 

And here is my Solpartmenu code:

<div id="HeaderPane" runat="server" class="HeaderPane" visible="true">
 <dnn:SOLPARTMENU runat="server" id="dnnSOLPARTMENU"
                                        separatecss="true"
                                        rootmenuitemcssclass="RootMenu_Static"
                                        rootmenuitemselectedcssclass="RootMenu_Selected"
                                        rootmenuitemactivecssclass="RootMenu_Active"
                                        rootmenuitembreadcrumbcssclass="RootMenu_Breadcrumb"
                                        rootmenuitemlefthtml="&nbsp;&nbsp;"
                                        rootmenuitemrighthtml="&nbsp;&nbsp;"
                                        usesubmenubreadcrumbarrow="false"
                                        userootbreadcrumbarrow="false"
                                        menueffectsmouseoverdisplay="none"
                                        cleardefaults="true"
                                        menualignment="left"                          
 />
</div>

Can someone tell me why there is background box in FF but not IE?