鼠标点击TextBox控件后清空默认字体

方案（一）

脚本：

<script type="text/javascript" language="javascript">

        //得到焦点时触发事件

        function onFocusFun(element, elementValue) {

            if (element.value == elementValue) {

                element.value = "";

                element.style.color = "";

            }

        }

        //离开输入框时触发事件

        function onblurFun(element, elementValue) {

            if (element.value == '') {

                element.style.color = "#808080";

                element.value = elementValue;

            }

        }

</script>

调用示例：

<tr align="center">

                  <td style="background-image:url('bg03.gif');background-position:center;background-repeat:no-repeat;height:69px">

                     <span style="color: #000000; font-family: 黑体;"><strong>用户名:</strong></span><asp:textbox id="UserName" Text="请输入用户名" runat="server" Width="100px" Height="20px" ForeColor="#808080"

                                            OnFocus="onFocusFun(this,'请输入用户名')"

                                            OnBlur="onblurFun(this,'请输入用户名')"></asp:textbox>            

                     <br />

                     <span style="color: #000000; font-family: 黑体;"><strong>密&nbsp;&nbsp;码:</strong></span><asp:textbox id="UserPass" runat="server" Width="100px" TextMode="Password" Height="20px"></asp:textbox>            

                  </td>

              </tr>

--------------------------------------------------------------------------------------------------------------------------------------------

方案（二）

[ 方法一]

前台代码：

<div>

    <asp:TextBox ID="txtName" runat="server"></asp:TextBox>

    <asp:TextBox ID="txtPwd" runat="server"></asp:TextBox>

    <asp:Button ID="btnLongin" runat="server" Text="提交" />

</div>

后台代码：

using System;

using System.Collections.Generic;

using System.Linq;

using System.Web;

using System.Web.UI;

using System.Web.UI.WebControls;

public partial class _Default : System.Web.UI.Page

{

    protected void Page_Load(object sender, EventArgs e)

    {

        //用户输入

        txtName.Attributes.Add("Value", "请输入用户名");

        txtName.Attributes.Add("OnFocus", "if(this.value=='请输入用户名') {this.value=''}");

        txtName.Attributes.Add("OnBlur", "if(this.value==''){this.value='请输入用户名'}");

        //密码输入

        txtPwd.Attributes.Add("Value", "请输入密码");

        txtPwd.Attributes.Add("OnFocus", "if(this.value=='请输入密码'){this.value=''}");

        txtPwd.Attributes.Add("OnBlur", "if(this.value==''){this.value='请输入密码'}");

        //

        if (!IsPostBack)

        {

            //内容

        }

    }

}

[ 方法二]

前台文本框里添加下面2个事件属性：

OnFocus="javascript:if(this.value=='提示文字') {this.value=''}"

OnBlur="javascript:if(this.value=='') {this.value='提示文字'}"

-----------------------------------例-----------------------------------------

<asp:TextBox ID="txtName" runat="server" Text="请输入用户名"

OnFocus="javascript:if(this.value=='请输入用户名') {this.value=''}"

OnBlur="javascript:if(this.value==''){this.value='请输入用户名'}">

</asp:TextBox>

<asp:TextBox ID="txtPwd" runat="server" Text="请输入密码"

OnFocus="javascript:if(this.value=='请输入密码') {this.value=''}"

OnBlur="javascript:if(this.value==''){this.value='请输入密码'}">

</asp:TextBox>