In addition to the design and structuring of the exhibit site, usability and accessibility are also necessary aspects to consider when building your project.
Usability means how effectively users can interact with and navigate a site.
Accessibility means how effectively users with disabilities or technological disadvantages (e.g., slow internet access) can use a site and how equivalent their experience is with the experience of users who do not have such challenges. Often steps taken to better serve the disabled also serve those who are technologically disadvantaged, e.g., video transcripts can serve the hearing impaired and those who do not have the internet bandwidth to play a video.
Visual Design - A good rule to follow is to keep it simple. A lot of different colors, decorative elements, and busy layouts can make the exhibit more difficult to navigate and the information more difficult to process. This is especially true for those with disabilities.
Page Organization and Layout - Breaking up the text into logical sections makes it easier to read. (Avoid having a "wall" of text.)
Headers - Use headers and subheaders to help logically break up the content on a page and to introduce/frame the information to come. This will make the page more readable and easier for screen readers to navigate.
Contrast - There needs to be strong contrast between the background and text. This means the colors need to have enough difference between them (both in intensity and hue) and that text is not on top of an image that makes it difficult to read. (There are browser extensions for checking contrast.)
Fonts - Avoid using ornate and difficult to read fonts and avoid using all caps.
Alt Text - Images should have alt text. Read more:
Captions - Videos should have captions.
Transcripts - Audio files (e.g., podcasts) should have transcripts; having transcripts for videos is also helpful and necessary if captions are not possible.
The following resources provide more helpful information on accessibility:
Web browser extensions list for checking accessibility, e.g., contrast and screen reader functionality