Newegg used to have a top-notch, no nonsense return policy like Amazon. But they changed ownership and over time the customer service has gone down hill. You can still return defective items without a restocking fee, but now they will charge you a restocking fee for problems that aren't their fault, for example if you buy a CPU cooler and it doesn't fit your case. I know this from personal experience.
However, Newegg does have third party sellers on the website and their return policies can be different from Newegg's. So using the same example if you bought a CPU cooler from Newegg's website but it is really a third party seller, that third party seller might accept a return for fitment problems.