Hi,
because you have selected a row to store in your session variable.
Session["divhtml_heading1"] = ds.Tables[0].Rows[0];
instead
Session["divhtml_heading1"] = ds.Tables[0];
use above code and iterate through all the rows,
although this is not the right way of storing data in session variable and display on your page. instead you can return List of your data and bind it with your page.
Let us know why you would like to store in session ? there should be some strong reason for storing information in session.
thanks
-Amit