Some points to follow:
Make sure there is a proper address and a landline telephone number on the webpage. Call the number and check that it rings at least.
If they only accept payment by a third party money handler such as Western Union, NoChex or PayPal, avoid. You need to be able to pay the company directly with your credit card.
Check the terms and conditions. Make sure they are not trying to avoid their legal obligations under the Direct Selling Regs and the Sale of Goods Act. If they state a restocking fee for returned items, buy elsewhere, also if they state no returns accepted.