Set the HTTP Headers for your template.
- status - input an HTTP Status code
- location - set a location for redirection
- content_type - set a Content-Type header
- terminate - set to "yes" to prevent any other output from the template
Do a 301 redirect {exp:http_header status="302" location="{path=site/something}" terminate="yes"}
Set a 404 Status header {exp:http_header status="404"}
Set the Content-Type header to application/json {exp:http_header content_type="application/json"}