常用input文本框内容自动垂直居中并默认提示文字单击为空

<input type="text" name="wd1" id="qy_1" maxlength="100" style="color:gray;width:199px;height:30px;line-height:30px;" autocomplete="off" value="请输入企业名称" style="color:gray;" onfocus="javascript:if(this.value == ‘请输入企业名称‘) this.value = ‘‘; this.style.color=‘gray‘;" onblur="if(this.value == ‘‘) {this.value = ‘请输入企业名称‘; this.style.color = ‘gray‘;}">