#1 Grammar and Spelling
Seems like a given, but we have all been to websites that just aren't quite up to par in the grammar and spelling departments. Where the unspoken acceptance of weak editing and proofreading in digital publishing came from is up for debate, but it speaks volumes about your company's credibility and professionalism. And it sends your customers searching elsewhere.
#2 Responsiveness
Not responsive in the traditional sense, but in the digital sense. In the digital world, your customers expect your presence on the web to be accessible and consistent with equal ease via their phone, tablet or computer. If you care about getting your message across to your customers as often as possible, you can't afford to have anything less than a responsive website.
#3 Consistent Presentation
Your graphics, fonts and other design elements must be consistent. Your customers want things as easy as possible and that means easy on the eyes and the brain. Consistency in your visuals, and your message, make your company easy to recognize, easy to remember and easy to do business with.
#4 Relevant Content
The days of keyword stuffing, fluff and filler are gone. Even the great Google has changed the way it searches because your customers demand relevant, valuable content and won't put up with anything less. So if you want your customer's attention, and their money, then you better provide useful information in your web presence.
#5 Ease of Use
Successful companies make it as easy as possible for their customers to connect to and learn about that company. Customers want to do business with companies that understand the value of their customer's time and their money. If I have to fill out a form just to find out if I want to do business with you, I'm already gone.