20 dB The background sounds are at least 20 decibels lower than the foreground speech content,
            with the exception of occasional sounds that last for only one or two seconds. Note Per the definition of "decibel," background sound that meets this requirement will
            be approximately four times quieter than the foreground speech content. Success Criterion 1.4.8 Visual Presentation Understanding Visual Presentation | How to Meet Visual Presentation (Level AAA) For the visual presentation of blocks of text , a mechanism is available to achieve the following: Foreground and background colors can be selected by the user. Width is no more than 80 characters or glyphs (40 if CJK). Text is not justified (aligned to both the left and the right margins).