I just did a site redesign to my template which go rid of graphical navigation replaced by CSS roll over text. There are now far few graphical elements which triples the page load time. An added benefit is I'm no longer dependent on javascript for my navigation. I have also fixed a ton of HTML coding errors. The primary remaining problem would be determining the proper DOCTYPE. I have added a few pages and the content is intact. These things should be good... But it has tanked my rankings in Google. Taking a major hit across the board. The pages are more easily spiderable (or should be). Is it common for these hypothetically good changes affect my rankings so dramatically? I had dominated the competition in Google with top 5 rankings in almost every relevant search term. Should I bounce back after the Google bot gets used to the changes? I welcome your thoughts.
This is purely anecdotal, but when I had my old site, which was 5 years old and was very highly ranked, I noticed that little changes here and here in the site layout DID affect the rankings. It's very strange, but they always inevitably come back sooner or later.