Change style of file upload button

<
asp:FileUpload id="File1"
runat="server"
style ="position: relative;text-align: right;-moz-opacity:0 ;
filter:alpha(opacity: 0);opacity: 0;z-index: 2;" />

<
asp:LinkButton ID="ImageButton1"
runat="server"
Text="Attach more"
style ="position: absolute;left: 166px; z-index: 1; " />