Creating an dynamically working ad banner

You can add controls dinamically on serverside.

On serverside you have to find first of all your placeholder. (for example: div, form)
After you can call your webservice and change the city and the other variables.
And the end of the process you can add a new LiteralControl to your placeholder.

You can use this as the follows:

Control myPlaceHolder = FindControl("form1");

String City = "your city";

String yourBanner = "<asp:label runat=server id=\"yourBannerLabel\" text="\" + City + "\"></asp:label>";

myPlaceHolder.Controls.Add(new LiteralControl(yourBanner));

I hope I could help you! Let me know if something is missing.