<input type="text" class="fl plsearch_txt" id="key" value="请输入关键字" onfocus="javascript:if(this.value==‘请输入关键字‘) this.value=‘‘;" onblur="javascript:if(this.value==‘‘) this.value=‘请输入关键字‘;">
Html+js 控制input输入框提示
原文:http://www.cnblogs.com/hwaggLee/p/4547478.html