Fatal Error

Fatal error: Call to undefined function get_header() in /usr/export/www/hosting/larumeurcourt/index.html on line 1.

Help, I don’t know what that means. I first had my own design, but it seemed like Worpdress couldn’t handle it, since it was homemade… Well now, I had put a new design, that is WordPress compatible, and it’s not working at all, please help.