403 Forbidden

I made a website on wordpress. It worked fine for 5 months but now it is creating problems. Most of the times, the message comes as “Forbidden

You don’t have permission to access / on this server.

Additionally, a 403 Forbidden error was encountered while trying to use an ErrorDocument to handle the request.”

Anyone knows why does it happen? I have consulted my hosting service. They correct the fault for time being but the problem occurs again and again. Now, the same message is coming and the site is not going to be active online. Do you know what needs to be done?Please help.