Dreaded 404 page for a very green newbie

Hello. I’ll start right off pointing out I know very little about coding. Yesterday I set up our new website http://www.complexpersonality.com. I got a few posts enetered, created categories, made the cataegories menu items and all was going well. I added the coding to use the google & bing webmaster tools and a few other items. Later, when I went back to the actual site, i found that if you click on the any of the actual posts, it goes to the “404” page. This had been working earlier, so I have absolutely no idea what I did to screw it up. Can anyone help me?

TIA

“MindSwirl”