In Islam taking percentage commission from both buyer and/or sellers on a website allowed? Like ebay.com

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.

Acting as a broker between the buyer and the seller is permissible whether this is on internet sale sites or else; what is important is that the broker should abide by Islamic rules while doing this. For instance he should not act as an intermediary for forbidden goods, like acting as a broker in selling intoxicants, pork, porn magazines or forbidden films and so forth, or to act in a transaction that is religiously forbidden, like transactions which include Riba (interest or usury); [all different types of Riba]. So if his work is free from helping in selling what is forbidden, or directing people to it, then there is no harm in taking a commission on this provided it is defined and specified.

Ibn Hajar said: 'Ibn Seereen, 'Ataa', Ibraaheem, and Al-Hasan did not see any harm in taking a commission for acting as a broker.' Furthermore, there is no harm if this commission is only given from the buyer, or from the seller, or from both of them, as in principle, it is permissible to give what is permissible to what is permissible.  

Allaah Knows best.