Whats a good website to buy manga from?

everytime i go to a bookstore there out of what i want. so does anyone know any good sites. i've heard of a href="http://www.animeniacs.com/index.php" rel="nofollow"http://www.animeniacs.com/index.php/a and a href="http://www.justmanga.com/" rel="nofollow"http://www.justmanga.com//a but i'm not sure if there dependable does anyone know if there dependable.