第一个问题:

RewriteRule ^products/([0-9]+)$ /products/$1/ [R]
RewriteRule ^products/([0-9]+)/$ /viewad.php?adid=$1

或更妙的是:

RewriteRule ^products/(\d+)/?$ /viewad.php?adid=$1

问题二:

RewriteRule ^africanews/(\d+)/(\d+)$ /africanews.php?app=view&func=viewcategory&categoryid=$1&page=$2