RewriteEngine on

# showarticle.php # 
# with or without trailing slash # 
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^([^/]+)/([^/]+)/?$ showarticle.php?parentarea=$1&area=$2 [L] 
# 
# this is always with trailing slash # 
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^([^/]+)/$ showarticles.php?parentarea=$1 [L,QSA]