Please follow the steps below to add MIME Types for your OpenCart site.
1. Log in to your hosting control panel (EG. http://cp.yourdomain.com)
2. Mouse hover to Web icon and click on Web Sites.
3. Click on your domain name.
4. Click on MIME Types tab.
5. Click on Add MIME button.
6. Fill in the following details.
Extension: .less
MIME-Type: text/less
7. Click on Update button to save the changes.
* Replace yourdomain.com with your actual domain name.