I've linked your other post to here, hope you don't mind. Its much better if you can keep everything to one post so that members can check on what you have tried and whether it has worked or not. here is your other post. click here
Not sure why your seeing the 404, I'm also seeing the same while trying to gain access to your site. :o(
I've just had a go at my first site also using FrontPage 2003. If you open your home page in your editor is it saved as index.htm That is what I chose to save mine as. I made the title of the page as 'Home' but in the save as box used the file ext. as above. This is what your browser will be looking for and if it can't find it then you will get the 404.
Sorry I can't offer much more help on this but I'm also right at the beginning of designing a website for the first time such as yourself.