Only small part of screen is clear at any one time
Use Gestalt Grouping Priciples to help guide eyes to appropriate areas
We are contrast detectors, make sure page and important elements have good contrast
Subltly can be lost
Use simple colors and make sure they tend to be of good contrast and bright
Though contast in color perception can help us see colors if well embedded, i.e., the absolute perception will change but the relative perception might work ok
What is on the screen is not predictable
Test on multiple monitors, including all device catagories you might think your study will work on
Test in bright environments if using images
Test under slow connections if using video
Make images and videos as small as you can without losing necessary details
Run a version of the experiment in the laboratory
Control lighting
Control connection speed, ideally run off of a hard drive