关于表单元素input的美化

<div class="cell">
<input type="text" name="Username" id="js-mobile_ipt" value="请输入用户名" class="text" maxlength="20"
onfocus="if (value =='请输入用户名'){value ='';this.className='text'}"
onblur="if (value ==''){value='请输入用户名';this.className='text'}" />
</div>
<div class="cell">
<input type="text" name="Password" id="js-mobile_pwd_ipt" value="请输入密码" class="text"
onfocus="if(this.value==defaultValue) {this.value='';this.type='password';this.className='text'}"
onblur="if(!value) {value=defaultValue; this.type='text';this.className='text'}" />
</div>
<div class="cell vcode">
<input type="text" name="Code" id="js_vcode_ipt" class="text" maxlength="5" value="输入验证码"
onfocus="if (value =='输入验证码'){value ='';this.className='text'}"
onblur="if (value ==''){value='输入验证码';this.className='text'}" />
<div id="code" class="code" onclick="createCode()"></div>
<span> <a id="js-mail_vcode_a" href="javascript:;" onclick="createCode()"> 换一张</a> </span>
</div>