Website preview displaying a bunch of ???????

When i try to preview my website, the only thing i see is a bunck of question marks all down the screen. at the very bottom it says Fatal error: Class 'ProjectConfig' not found in /home/alphaa6/public_html/index.php on line 12.
in my index.php on line 12 it says : ProjectConfig::setup(); . Im not sure what the issue is or why this error is occuring. any help is appreciated.