A lot of website I see try to explain this in a very complicated manner. So, to be the nice guy I am, I will try to summarize it all up. Do you see those little sections I have on the side of this site? Well,say a case scenario is that I made a mistake a whil ago and forgot about it. Well, after making all these pages, I would have to go back and fix them all, or use SSI.

SSI (server side includes) Is something all webmasters use, and is no secret. You use a little strand of code it looks like :
<.!--#include virtual="file.html" --.>
Just write the filname of you info, and put it anywhere on your site. it is recommender for things on most of the pages and that is updated alot. Like the poll to the left of the screen. And if you make a mistake, just go back to the indiviual file and correct it once, and they will all be correct. To break it down for you...

1.first you make alayout, like the one you see

2. Then you name all your sections, and instead of making links, use the code you see above.

3.then make a seperat file, with all the links for one section.

4.put the code on every page the layout is on.

5. If you make a mistake, just go back to the indivual file and all of the content on every page will be corrected.

Now that you have this go use it!!!