Hi digital,
I use include files for common areas on my site so I only have to update one file instead of updating each page. So my top, left, right and bottom areas are all include files.
So basically you create a file named rightSideAds.html and put only the ad code on this page. Then you call up this page from any page you want to display from using the "include HTML" code.
Here's a good tutorial for setting this up....
http://webmaster.iu.edu/tool_guide_info/ssi.shtml
Notice the instructions say you must use .shtml extensions instead of .html. You can modify your .htacess file on your server (located in your root directory of your web server where your index.html is located.) so you don't have to change the file extensions of your pages and keep everything .html
Open your .htacess file on your Web server in Notepad or another ASCII text editor and add the following line at the very bottom...
AddType text/x-server-parsed-html .html
That line will interpret .html pages as .shtml so you don't have to go and change the extensions on your 17 pages and lose any of your rankings with the search engines. One caution I've read is that doing so can affect the load on your server. I've been using this for over a year and haven't had any problems but just wanted to warn you.