If you do nothing else to improve your web pages, you should make them load as fast as possible. Users will leave your site if it loads slowly.
Writing for the web is different from writing for print. People skim online, especially when they first get to a page. You want the contents of your page to give them what they want quickly, but provide enough detail for those who want expansion on the basics.
Many people are not tolerant of spelling errors. People judge websites by the quality of the writing, and spelling and grammar errors are an obvious indicator of quality for many people.
One of the key things to focus on is to make the site as easy to use and user-friendly as possible.
Broken links are another sign for many users (and search engines, too) that a site is not maintained. It's important to use an HTML validator and link checker to help you check older pages for broken links.
Contact information reminds people that the site is maintained by another person. This means they may be more charitable and more willing to respect you when they do make contact. Plus by putting contact information on your site, you are helping your readers trust you. If there is an email address or phone number, they know they can contact you if there's a problem.
And, if you do have contact information on your site, follow up on it. Answering your emails is the best way to create a long-lasting customer, especially as so many email messages go unanswered.