With SSI you can have a certain thing on all your pages. SSI makes it alot easier to add links since lets say you have tables and you add something, you will need to go to each page to add that link and that gets tiresome. To start things of you need to make a page. When your page is done and you want to use ssi here is what you do. Now paste it on note pad and save it as lefttable.txt after that save it again but choose the save as option and save as lefttable.html.
Next step go back to the original page that has everything.
Next upload the lefttable.html, middle.html, and the middle.shtml once that is done all you need to do is go to you site. Thats all there is to it, the next things is what you use to build your site. Do you use FTP or online editor, like angelfire, tripod.