What makes a website design good?

What stops visitors from leaving a webpage? (Or what makes visitors leave a webpage?)
What web design invites users inside a website?
What prompts visitors to buy?

Image Factory abides by 10 elemental rules of effective website design (not necessarily in that order):
1. Usability: website design should be user-centric for successful and profit-oriented web design.
2. Quality: high-quality text and photo content are as important as the design that supports them.
3. Focus: website design should streamline users’ attention, leading them to the goal, sale or product.
4. Visibility: effective use of text, colors, and graphic elements should define key interest points at a glance.
5. Simplicity: web page design should help users instantly find the sought information or product
6. Spacing: allowing balanced, calculated spaces ensures the strongest page content visual impact.
7. Organization: logically structured web page content and navigation leads to quick conversions.
8. Optimization: web pages should be universally compatible, lightning fast, and crawler-friendly.
9. Moderation: range of creativity and inventiveness should be justified primarily by scope and function
10. Testing: a successful website design should be determined by the end user, not by us or our clients.