The seller of the item. If you do not see a link to ‘message seller’ on the listing page, or a button to buy/bid then make sure the listing is still active.  Look at the top of the listing for a red banner with yellow text that says ‘this listing is no longer available or has been sold.’ If an item has sold, you can not contact the seller. If the listing is still active but you still can’t message the seller, look for a yellow box with a Yellow Triangle to the right of the listing photos that says “This seller requires that you use our verified address page…” which means you need to be a verified member before contacting the seller.