A question about seeds??

I'm on my third grow. I'm using a normal closet with 400w hps growing in grow mix. I have been fairly successful. I started in November with a bunch of seeds a friend gave me. I grew them took cuttings from them. Grew those took more cuttings. I figure I will have enough bud to last me awhile after this harvest so i'm going to chill for awhile. My question is how safe is it to buy seeds on-line? When I start up again I was thinking of purchaseing some seeds and trying some different varities. I also plan on building a desent grow box instead of using the closet. I have learned a tremendous amout of info on here and continue to learn stuff every day. Thanks