example:

Code: 
url.rewrite = (
"^\/(.*)\/$" => "/index.ph?mr=$1",
"^\/$" => "/index.php"
)
add this to lighttpd.conf

or if you want to make it just for a specific domain then like this:

Code: 
$HTTP["host"] =~ "(^|\.)yourdomain\.com$" {
url.rewrite = (
"^\/(.*)\/$" => "/index.ph?mr=$1",
"^\/$" => "/index.php"
)
}