QSA or Query String Append

QSA is flag used in .htaccess to append query string in traditional format into formatted or over written url after the URI has been rewritten. For example you are rewrite url from http://www.example.com/index.php?id=foo&user=bar to http://www.example.com/foo/bar and now you want to pass traditional query string to this over written url like http://www.example.com/foo/bar/?action=success then you have to declare following rule in .htaccess like RewriteRule ^([A-Za-z0-9]+)\/([A-Za-z0-9]+)$ index.php?id=$1&user=$2 [QSA]