The default home page needs to have a specific file name determined by the admistrator of the server the site is on.If you create your site in FP by doing File > New > Web, FP will create a site with a true default home page. When you publish that web to another server, FP will check the server to see what the default home page needs to be named. It will then update the file name of your default home page and all links to it accordingly.
If you didn't start out this way then you can open the live site up the same way you open a local one. File > Open Web > type in http://www.ulr.com. You can then create a folder in this web. Then click on the new page icon on the FP tool bar while inside that folder. The filen name FP gives to that page is the correct default home page file name for your site.
You can the just rename your home page to match that. FP will update all the links to your home page accordingly.