As a mattress manufacturer, we of course suggest buying in store because you can try out not just one, but several mattresses. You spend a great deal of your life in bed, so you want to make sure that you are getting exactly what you want. That said, you could also try other items as well, such as pillows or pillow tops. We do understand that this method may not work for everyone, though. It can at times be overwhelming if you have tried out many beds, to remember which one had the firmness or other attribute you liked. 

Often, shopping for mattresses online, if you don't like it, you can return it. It depends on the company, though. Some take the mattresses back at no cost to you, others do, even if it is a small fee. Some donate the returned mattresses to charity, others resell them or dispose of them. Some provide packaging to return it in, others do not, so that expense falls on the consumer. We suggest reading the fine print if you're going to buy a mattress online, so you know exactly what you are purchasing, if there will be a cost to return it and where it will be going if you end up returning it.