500,000 posts...

The URL up the top there says "post502177".. does this mean 500,000 has already passed us by?

Yes and no. The post numbers include all of the spam and stuff that gets deleted, so we have passed 500,000, but we do not actually have 500,000 posts.

The number on the front page is how many posts exist in the system.

Do you mean comments through the rep/comments mechanism or actual posts?

I counted both:
In posts: 133
In rep/comments: 5,007