Error occured!

Error ID: #E-7
More info: Cannot load class DOMDocument, file ./classes/domdocument.php doesn't exist

File: /var/www/html/system/load.init.php Line: 14
File: /var/www/html/classes/vocations.php Line: 13
File: /var/www/html/classes/website.php Line: 157
File: /var/www/html/classes/website.php Line: 163
File: /var/www/html/system/load.compat.php Line: 86
File: /var/www/html/index.php Line: 36