I learned of SSI (Server Side Includes) long before I built my current site. Since it seemed only way to go, I checked it out once again for new site to be. What SSI amounts to is creating a new page for any elements common to all pages on your site. Then ask server to include these pages whenever main pages are requested.
For example, build a regular HTML page containing all content, including graphics, as is often used in left column of a page as basis of navigation. Then, instead of adding this content to each page, simply include file. And hey, it's super. If you need to make a change, you make it only once, instead of on every page on your site.
SSI Slows Page Downloads?
What prevented me initially from using SSI were notes I read regards increasing page download time. Each page using included files needs to parsed (read) by server to find any files to be included. Being an absolute fanatic about minimizing page download speed, I passed. Bad mistake.
Updating Multiple Pages Chews Up Time
Six month later, changing a single menu item was taking hours. I decided to ignore page download time and go. But I ran into another snag. Pages with includes need SHTML extension, else server won't parse them. (An S in front of HTML.)
Switching From HTML to SHTML Busts Links
Nuts. I already had lots of incoming links. Since I didn't want to bust them by changing file names, I passed once again.
I had heard people speak of ways in which a server in some cases could be instructed to treat HTML pages as SHTML pages. But I didn't check it out. Another bad mistake.
The Perfect Solution
Many months later I ran across following code. Add these lines to top of your .htaccess file, and all existing HTML files will be parsed just as if they had .SHTML extension. Neat. No changes in file names, which means no busted incoming links.
Options Includes AddType text/html .html AddHandler server-parsed .html
.htaccess is a hidden file in root directory on your server. It is helpful in doing many things, and can be located elsewhere as needed, but for now let's focus on above.
In WS_FTP, when you type -al into blank field to right, this file name will become visible. The best plan is to download file, add above code, then upload and overwrite original. (The reason for downloading first is to be certain you hold whatever file may already contain.)
Creating Files
What I did next was create a file, yleftnav.html, containing all content in left column of a page. Then on each page, I replaced content in that column with following.
Given three lines above in .htaccess file, each .HTML file is parsed for include command. When found, content of file is included in page at that point. You can see results by viewing source for one of my pages. And you can view file included with ...