前台：需要在前台界面将div元素转化为服务器控件，如下标红处
<div id="div_out" runat="server" style="margin-top: -45px; float: right;" visible="false">
<a class="btn_addPic" href="javascript:void(0);" style="margin-top: 5px;"><span><em></em>上传文件</span>
<input class="filePrew" id="file1" title="支持.doc,.docx,.xls,.xlsx,.zip,.rar,.png,.jpeg,.gif,.jpg,.txt格式，文件小于5M" οnchange="show1()" tabindex="3" type="file" size="3 " name="pic" runat="server" /></a>
<input type="text" id="Txt1" class="tx_zdw_150" />
<asp:Button ID="Button2" runat="server" CssClass="so" Text="Excel导入" OnClick="Button2_Click" />
<asp:HyperLink runat="server" ID="lnk" Target="_blank" NavigateUrl="~/emergency/Files/应急队伍.xls" CssClass="so1">点击下载模板</asp:HyperLink>
</div>
后台：在初始化时或者事件中就可以调用了
div_out.Visible = true;