Display:table Column title hover is not working

i m using display table library for displaying bulk of records with pagination. But in this table i m not able to show Column heading name while while hovering mouse on column grid. title attribute is already there in tag. How to make this.

Here is my code , but not able to get.

<display:table name="requestScope.numberList" id="num" width="100%">
   <%   MobileBean mb=(MobileBean)num; %>
<display:column title="Student Name" > 
             <%= mb.getSName(); %>
</display:column>
<display:column title="Mobile No" > 
             <%= mb.getSMobileNo(); %>
</display:column>
<display:column title="Status" > 
             <%= mb.getStatus(); %>
</display:column>
</display:table>