This is usually caused by not having a home page file inside of your www directory. Once you upload your homepage file into this directory, the error message will go away and your new home page will load. If you have not uploaded your page to the public_html directory, then you will not see it!
When you upload your index.html page, you will need to delete or overwrite our “under construction” page currently there. If you upload an index.htm page, you will not be able to see it automatically at your site until you delete the index.html page. Here is a list of “priorities” of pages. This means, for example, if you have an index.htm page as your home page, and there is also an index.html page, the index.html page will be what is “seen” when someone goes to your site.
default.html, default.htm, index.phtml, index.php, index.cgi, index.shtml, index.html, welcome.cgi, welcome.html, index.htm, index.asp, homepage.html, homepage.htm and homepage.cgi