Making changes to Joomla’s core files is often neccessary, but there’s a right and a wrong way to do it.
The WRONG way is to directly edit Joomla’s files. If you do, you’ll lose all your changes when you next update your site.
The RIGHT way is to use a layout/template override
The following is a list of informative resources to help you understand what layout/template overrides are in Joomla – and how you can use them to customize your JoomlArt Template based site . . . .