5
as Mantooth said, just delete the content inside the templates_c folder. You should leave the index.html since it works as an *small* security-layer. If you accidently delete it you can copy the index.html from another folder.
The templates_c folder stores your compiled theme as well as Smarty templates for XOOPS and any third-party modules you've installed, you can safely empty it's content.
Best Regards,
Bananadude
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