#------------------------
<IfModule mod_rewrite.c>
  RewriteEngine on
  RewriteRule ^(.*)$ index.php?n=$1 [L,QSA]
</IfModule>
$-------------------------

1. http://www.mysite.com/services/seo-work
2. http://www.mysite.com/services/online-editor

if(IsFoundPageInDirectory(online-editor.php))
{
   GoToUrl(http://www.mysite.com/services/online-editor.php)
}
else
{
   GoToUrl(http://www.mysite.com/services/index.php?s=seo-work)
}

<IfModule !module>
  # some directives
</IfModule>

<IfModule module>
  # other directives
</IfModule>

<IfModule mod_rewrite.c>
  RewriteEngine On
  RewriteCond %{REQUEST_FILENAME} !-f
  RewriteCond %{REQUEST_FILENAME} !-d
  RewriteRule . index.php [L]
</IfModule>

<IfModule mod_rewrite.c>
  RewriteEngine on
  RewriteCond %{REQUEST_FILENAME}.php -f
  RewriteRule ^([^/]+)/$ $1.php
  RewriteCond %{REQUEST_FILENAME} !-f
  RewriteRule ^(.*)$ index.php?n=$1 [L,QSA]
</IfModule>