...
Don't lock content to either portrait or landscape presentation.
See more detailed information on how to comply with these requirements.
Page Flow
Content must be presented without loss of information or functionality, and without requiring scrolling in two dimensions for:
Vertical scrolling content at a width equivalent to 320 CSS pixels;
Horizontal scrolling content at a height equivalent to 256 CSS pixels.
Please see more detailed information on how to comply with these requirements.
Resizing of Text
With the exception of captions and images of text, text should be able to be resized without assistive technology up to 200 percent without loss of content or functionality.
Paragraph Sizing
There should be no loss of content or functionality when the user adapts paragraph spacing to 2 times the font size, text line height/spacing to 1.5 times the font size, word spacing to .16 times the font size, and letter spacing to .12 times the font size.
Text Spacing
Some people need text with different spacing or font characteristics.
...
In content implemented using markup languages that support the following text style properties, no loss of content or functionality occurs by setting all of the following and by changing no other style property:
...
Exception: Human languages and scripts that do not make use of one or more of these text style properties in written text can conform using only the properties that exist for that combination of language and script.