>Hi,
>
>I am beginning a new project, add-on, to my existing ASP.NET Web Forms project (VS 2015). I am looking at how my "old" pages work but want to use a more modern approach for the new project pages.
>
>The first thing is the block of text appearing at the top of the page. The text comes from a file header.inc (where the text can be customized by each customer). The way I show this block of text at the top of the page in the old page is as follows:
>
>

>		<table class="HeaderText" align="center" border="1">
>				<tr>
>					<td>
>						<p><!--#include File="header.inc"--></p>
>					</td>
>				</tr>
>			</table>
>

>
>What class or HTML element you would suggest I use that can be made responsive with Bootstrap?

Depends what you want your site to look like :-} Maybe something as simple as:

<div class="container">
    <h1 class="text-center">><!--#include File="header.inc"--></h1>      
 </div>