It is common magento issue. You open product page and have quantity set to “0”. This is not good. Customer think that if the quantity is 0 it normally means nothing will be added to the cart. Setting default product quantity to 1 make your site more user friendly.
It is pretty easy to fix. You do not need any programming skills.
- Go to Admin Panel -> System -> Configuration -> Inventory-> Product Stock Options from the Menu.
- Click on Add Minimum Qty button (next to Minimum Qty Allowed in Shopping Cart option).
- Choose Customer Group: ALL GROUPS as you want this to be applied to all users.
- Enter 1 for Minimum Qty.
- Save Config.
You can set different minimum quantity value for different user groups. Say for wholesale group it can start from 100.