用javascript实现的激活输入框后隐藏初始内容

<div>
<label for="email">Email</label>
<input name="email" type="text" id="email" style="width:134px;" onfocus="if（this.value==’Input your email’）this.value=’’;"onblur="if（this.value==’’）this.value=’Input your email’;" value="Input your email" />
<label for="pwd">Password</label>
<input name="pwd" type="password" id="pwd" style="width:132px;" onfocus="if（this.value==’inputpass’）this.value=’’;"onblur="if（this.value==’’）this.value=’inputpass’;" value="inputpass" />
</div>