1. Use web safe colors, so that your design is shown as you want
You can check the web safe color here
http://www.permadi.com/tutorial/websafecolor/
2. Test your web pages in different types and versions of web browsers
You may test it with
http://browsershots.org/
3. Keep graphics files small.
This is a tools for image optimization
http://www.sitereportcard.com/imagereducer.php
4. Ensure your website display well with different types of screen resolution
http://www.yournew.com/resolution_test.cfm
5. Make your webpage load faster. Don’t put too much graphics or other objects
You can test your webpage speed here
http://www.selfseo.com/website_speed_test.php