I have heard that you can create an external file for your site navigation that would allow you to make a change to one file and that change would popolate throughout all of the pages referencing that file. I have heard this called an ""include"" file or somthing similar.

Would anyone know how to go about creating this or maybe where some tools would be to do this easily? I suppose the reason for it being an external file would be for the search engines, is that correct?

thanks in advance for your help!

that is called SSI - server sided includes. If your host supports server sided includes, you can use a file which can be just included in other files using <!--#include file--> (exact syntax I forgot )

If you are using any programming language such as ASP or PHP also it can be done.

Offline tool is available in macromedia dreamweaver called - Library which can be updated in all the files which uses in a fly.

For search engines, I haven't heard any..