Web Accessibility 101
Write Clearly and Simply
Clear and simple writing must be presented so it is understandable by the audience.
Use Headings Correctly
Do not use text formatting, such as font size or bold to give the visual appearance of headings - use actual headings logically (Heading 1, Heading 2, Heading 3, Heading 4, etc.) for all content headings. Likewise, do not use headers to achieve visual results only.
Use Lists Correctly
Do not use characters (such as -, *, ), tab key, or spaces to create the illusion of a list. Use the unordered or ordered list buttons. Unordered lists should be used when there is no order of sequence or importance. Ordered lists suggest a progression or sequence.
Image
Content and functional images must have appropriate and equivalent alternative text. Decorative images do not require alternative text.
Links
Link text should make sense when read out of context. Don't use click here, here, more, read more, link to [some link destination], info, etc.
URLs as link text should be short and easy to read.
Images used as links. The image's alternative text should convey the content of the image and the function of the link.
Links should look like links, and nothing else should. Users are accustomed to seeing links underlined.
Video and Audio
Captions and transcripts must be provided for video and audio.
Color
Do not use color alone to convey meaning. Make sure information conveyed with color is also available without color.
Make sure color contrast is strong, especially between text and background.
Animations
If you must include animations that blink or flash, make sure the screen flicker does not occur between frequencies 2Hz and 55 Hz.
Tables
Keep your data tables simple and identify row and column header cells.
Complex data tables will need to be coded using advanced HTML techniques.
Do not use bold to indicate a header cell in data tables.
Avoid data tables with more than two levels of row and/or column headers.
Avoid spanned rows or columns.
Avoid using tables for layout.
Documents
Everything listed above applies to documents.
Ensure Adobe PDFs are tagged. The accessibility of the PDF depends on the accessibility of the original document (MS Word, MS PowerPoint, InDesign, etc.). Not only does the underlying tagged document structure make it possible for a screen reader to properly read a PDF out loud it also makes it possible for a mobile device to correctly reflow and display the document on a small screen.