Autowidening DropDownList (IE only!)

<asp:DropDownList ID="ddl" runat="server" Width="100px" onmouseover="this.style.width = 'auto';" onfocus="this.hasFocus = true;" onblur="this.style.width = 100; this.hasFocus = false;" onmouseout="if (!this.hasFocus) this.style.width = 100;" />

Works in Internet Explorer only - in Firefox the control does not narrow back.