Hi pavan,
you can try this one. I have tried it with background colour, and it worked. hope it will work with yours also.
Take a Repeater to show the message. And the only thing you have to maintain is the text-align, style property of the div. Here is the solution.
<asp:repeater id="Repeater1" runat="server" xmlns:asp="#unknown">
<itemtemplate>
<div style="text-align:<%# Eval("align")%>">
<%# Eval("message") %>
</div>
</itemtemplate>
</asp:repeater>
You need to get another column
align. put the value of this in your stored procedure as the chat of admin or user (left & right).
try it..hope it will fixed your problem.