求2个JavaScript!

<html:form action="deleteUserAction.do" method="get">
<div align="center">
<table width="681" height="69" border="1" bgcolor="#dff1f9">
<tr>
<td height="28"><div align="center"><bean:message key="struts.addjsp.userId"/></div></td>
<td width="101"><div align="center"><bean:message key="struts.addjsp.userName"/></div></td>
<td width="91"><div align="center"><bean:message key="struts.addjsp.age"/></div></td>
<td width="91"><div align="center"><bean:message key="struts.addjsp.sex"/></div></td>
<td width="158"><div align="center"><bean:message key="struts.addjsp.email"/></div></td>
<td width="118"><div align="center"><bean:message key="struts.addjsp.qq"/></div></td>
<td width="118"><div align="center">删除用户</div></td>
</tr>
<logic:iterate id="all" name="user">
<tr>
<td width="82" height="28"><div align="center"><bean:write name="all" property="userId"/></div></td>
<td><div align="center"><bean:write name="all" property="userName"/></div></td>
<td><div align="center"><bean:write name="all" property="age"/></div></td>
<td><div align="center"><bean:write name="all" property="sex"/></div></td>
<td><div align="center"><bean:write name="all" property="email"/></div></td>
<td><div align="center"><bean:write name="all" property="qq"/></div></td>
<td width="118">
<div align="center">
<html:multibox property="deleteId" value="${all.userId}">
</html:multibox>
</div></td>
</tr>
</logic:iterate>
</table>
<html:submit property="action">
<bean:message key="struts.addjsp.button.add"/>
</html:submit>
<html:reset property="action" value="重置">
</html:reset>
<html:submit property="action" value="全部删除"/>
</div>
</html:form>
第1个:如果用户没选择<html:multibox>就按了<html:submit property="action">
<bean:message key="struts.addjsp.button.add"/>
</html:submit>就出现个"请输入要删除的信息"
第2个:按<html:submit property="action" value="全部删除"/>后<html:multibox>就全部选中了
这2个JavaScript应该怎么写呀?