This page is used to test the proper operation of the HTTP server after it has been installed. If you can read this page it means that the HTTP server installed at this site is working properly.
If you are a member of the general public:
The fact that you are seeing this page indicates that the website you just visited is either experiencing problems or is undergoing routine maintenance.
If you are the website administrator:
You may now add content to the directory public_html. Note that until you do so, people visiting your website will see this page and not your content. To prevent this page from ever being used, delete index.html in /public_html.