If I have a number of values stored in a text file and I want these values to be loaded into an HTML file, what is the simplest way to go about this?

Do you mean load them up dynamically (ie. every page load)? HTML alone doesn't have the ability to do this, you'll need a server side language like PHP, Perl or ASP.

The simplest way would be to edit the text file to javascript syntax, rename extension to ".js" then treat it as an external.js
By including the tag <script language=javascript type=text/javascript src="path to external.js"></script> your vars will be loaded into the html page.