ranking problems after changes [migrated]

The site has been up for 5 years with little change and has been on the second/third page. I added a couple of pages and altered and added to update the info. I added a couple of links to suppliers. For a couple of days the ranking improved even onto page 1..now however after 5 days the ranking has fallen dramatically. At the same time I also started a small ADWORDS campaign. Is the fluctuation in ranking to be expected or have I made some basic error? thanks