All interactive elements should indicate when they’re focused so that users know which element they are currently interacting with. This is where focus styles come into play.
The heading levels (1-6) are often considered a way of describing and determining the “importance” of a heading, with h1 being the most important.
Paragraphs of text are a fundamental core of web content. It's important to display them in a fashion that is optimally readable to the majority of your audience.
When text is presented as an image of text, that limits peoples' ability to change the appearance of that text. So wherever possible, use text along with CSS to apply styling.
Users can find their way around a web site more easily and confidently if they know where they are.
Icon fonts are a popular and effective method for providing scalable symbols that can be used to label controls and provide graphical information. The information provided by icons also needs to be available to people who can’t see them.
A clear indication that specific form fields are required can save users time and avoid potential errors relating to missing data when a form is submitted.
People with a variety of print disabilities (including low vision, dyslexia, other cognitive disabilities) can benefit from being able to increase the spacing between lines, words, and/or letters on their own device.
Use responsive design to allow your content to zoom and respond to various screen sizes.
Color is a powerful visual means of presenting or distinguishing information, but when you use color to identify or distinguish information, make sure that this information is still available to people who can't perceive color.
Avoid referring to a button, menu, or other item in the page only by its position on the page; instead, use additional information that describes the content.
Headings are used to group and label sections of content, giving visual structure to the page and providing a means of navigation to screen reader users.