If you need a simple online htaccess checker that can validate that your .htaccess lines are free of any syntax errors, then you can try http://www.htaccesscheck.com
Simply either paste your .htaccess lines in the box at the site or upload your .htaccess file and get a report about:
- Any syntax errors in your file, including line number and reason.
If OK, you will see this :
Enjoy!!