I should have paid more attention to this forum... learned lots about other things, but just now learning about SEO. I hear it's a bad idea to change any WHOIS data, particularily for Google's sake. Since G likes older sites without WHOIS changes, what happens if you update JUST the email address? I had to... it was for an email address I no longer had. The new one I entered should be good for a long time.
Also, I made a website about two years ago for a friend's business. Got her up to a PR4 and a HUGE increase in traffic. Since my web design skills are much improved, I redesigned her website replacing .htm (and .html on the index page) with .php throughout (only for php includes - navigation, header, footer, etc - NOT a database driven website). I saved the old URLs (like mysite.com/pricelist.htm) and put the logo, with a message stating the page has moved, and included an HTML link to the new page (like mysite.com/prices.php).
It's been about a month and traffic to the site has dropped off - about the same time the new site was launched. The update to the email address was just this week. Have either of those likely hurt the seo? If so, how bad could it be?