仿Ext的textarea单击默认值消失

<textarea id="other" name="other" cols="50" rows="5"
    onblur="if(this.value == ''){this.style.color = '#ACA899'; this.value = '在此处填写备注'; }"
    onfocus="if(this.value == '在此处填写备注'){this.value =''; this.style.color = '#000000'; }"
                                style="color:#ACA899;">在此处填写备注</textarea>