We do have a default 404 page that can be replaced in a few seconds with your own. We recommend doing this to help maximize your traffic. A 404 page is what loads when someone visits a page on your site that does not exist. If you aren't sure how to apply your custom 404 page to your website, please visit our page on custom error pages.
We do create a default.html page that acts as a placeholder for your site, until you upload or create your own website.