Below is the list of web design and usability guidelines with "relative importance" rating of 5 (based on rating of 1 to 5).
Use an Iterative Design Approach
Provide Useful Content
Use Black Text on Plain, High-Contrast Backgrounds
Ensure Visual Consistency
Provide Consistent Clickability Cues
Use Clear Category Labels
Ensure Usable Search Results
Ensure the Homepage Looks like a Homepage
Do Not Use Color Alone to Convey Information
Eliminate Horizontal Scrolling
Allow Simple Searches
Create a Positive First Impression of Your Site
Organize Information Clearly
Display Information in a Directly Usable Format
Detect Errors Automatically
Put Critical Information Near the Top of the Website
Do Not Display Unsolicited Windows or Graphics
Label Data Entry Fields Clearly
Use Unique and Descriptive Headings
Distinguish Required and Optional Data Entry Fields
Evaluate Websites Before and After Making Changes
Minimize User Data Entry
Format Common Items Consistently
Provide Feedback on Users' Location
Set and State Goals
Show All Major Options on the Homepage
Provide a Search Option on Each Page
Design for Common Browsers
Put Labels Close to Data Entry Fields
The above web design and usability guidelines are useful for web designers and web master in the design and development of website/portal which is high in usability.
