urbanoid

I solved it!

* This plug-in helped me to make category menu different: https://www.ads-software.com/extend/plugins/advanced-permalinks/

* And I had to put these lines into the .htaccess file:

# BEGIN WordPress
RewriteEngine on
RewriteBase /
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^houses$ ?cat=1 [L]
RewriteRule ^lands$ ?cat=3 [L]
# END WordPress

For advanced wordpress 3 themes and tutorials, check out my wordpress 3 theme blog.