Many servers and server software support Server Side Includes or SSI. Ask your server if they support it. If so you can load a text file into as many web pages as you want. To learn more about SSI I would suggest visiting: http://www.omsi.edu/~rosso/xssi/
Also make note that on my commercial site there are links to resources for web masters, and one or two of them is about SSI. When you hit my site just hit the button that says INFO.