Your website is as good as the weakest part of it, whether it is the hosting server, graphics, content, images, navigation, and so on.
Is your website slow?
It can be very frustrating to experience a website that loads slowly, or even times out. Your visitors will not wait more than 3 seconds before they opt out and visit another website instead.
Is the information to complicated to find?
If a new customer can't find what he/she is looking for in ONE click (max two) they will give up on you. They expect to find anything they are looking for easy and seamless.
Where is the contact information?
If you got a visitor that does not find how to contact you, that visitor will never be converted to a customer.
Is the website secure?
Encryption/ Https is to ensure the data between the web server and the web browser is secure.