My site is showing up for my major keyword phrases in Yahoo and MSN but I'm nowhere to be found in Google. Why does Google hate me? (Or alternatively, my site was doing well on Google but its rankings have suddenly plummeted. Am I penalized?)

If you're going to be in the SEO biz, or even if you're just trying to get your own personal business site more exposure in the search engines, you need to realize that rankings (and the traffic they may bring) are not static. You may get comfortable seeing your site rank highly for your most coveted keyword phrases, but don't ever assume it will remain there forever.

Sites do not get penalized or banned unless something has been done which deceives the search engines. Deception generally comes in the form of hiding stuff or trying to artificially inflate link popularity. If you're not playing games with the engines, then you don't ever have to worry about penalties. If your site is suddenly gone, it's most likely because of a major algorithm shift. The search engines are constantly tweaking their algorithms, and new sites are always being created, so ranking fluctuations are part of the normal course of business.

Because of this, it is crucial to optimize your site for lots and lots of related phrases. This will ensure that when some phrases go AWOL, the others will perform well for you. I can't stress enough how important this strategy is to your SEO campaign, as well as your piece of mind. Never be married to any 1 or 2 specific phrases. Yes, it's cool to rank highly for the most coveted ones, but if they're that important to you, then you should purchase PPC ads that are triggered by them.

The best advice I can give you is to change your mindset from "rankings" to "targeted traffic and conversions." I know I sound like a broken record with this, and it may even seem like a convenient excuse; however, if you don't want to make yourself crazy, it's best to ignore rankings, and instead work hard at making your site better and better. While your various keyword phrases are on an emotional roller coaster at Google, you won't even notice a blip in your traffic or sales if you've got all your bases covered. It may be clich�, but it really does work and it does pay off in the long run