//here is the javascript for show and hide
<script language="javascript" type="text/javascript">
function onover()
{
document.getElementById('<%=Label1.ClientID%>').style.display="inline";
}
function onout()
{
document.getElementById('<%=Label1.ClientID%>').style.display="none";
}
</script>
//calling the javascript onmouseover and mouseout
<asp:Button ID="Button1" runat="server" Text="Button" onmouseover="javascript:onover(this);" onmouseout="javascript:onout(this);"/>
<asp:Button ID="Button2" runat="server" Text="Button" onmouseover="javascript:onover(this);" onmouseout="javascript:onout(this);"/>
mark it solution if this is your solution.
Thanks
Ashish