input type:text输入框点击输入，文字消失

<input name="Header1$txbsearch" type="text" value="18912345678" id="Header1_txbsearch" class="txbindex" onfocus="if (value =='18912345678'){value =''}" onblur="if (value ==''){value='18912345678'}" style="color:#999999;" />