Guide to Guideline 2.3 Level 1 Success Criterion 1

• Content that violates international health and safety standards for general flash or red flash is marked in a way that the user can avoid its appearance. [V]

2.3 L1 SC1

Key terms and important concepts

general flash threshold

• A sequence of flashes or rapidly changing image sequences is not permitted when both the following occur:

  1. the combined area of flashes occurring concurrently (but not necessarily contiguously) occupies more than one quarter of any 335 x 268 pixel rectangle anywhere on the displayed screen area when the content is viewed at 1024 by 768 pixels and

  2. there are more than three flashes within any one-second period.

  NOTE: For the general flash threshold, a flash is defined as a pair of opposing changes in luminance (i.e., an increase in luminance followed by a decrease, or a decrease followed by an increase) of 20 candelas per rectangle meter (cd.m^-2) or more and where the screen luminance of the darker image is below 160 cd.m^-2.

NOTE: Thresholds are based on ITC Guidance Note for Licensees on Flashing Images and Regular Patterns in Television (Revised and re-issued July 2001) as modified by the Wisconsin Computer Equivalence Algorithm.

red flash threshold

• A transition to or from a saturated red at any luminance level is not permitted when both of the following occur:

  1. the combined area of flashes occurring concurrently occupies more than one quarter of any 335 x 268 pixel rectangle anywhere on the displayed screen area when the content is viewed at 1024 by 768 pixels and

  2. there are more than three flashes within any one-second period.

  NOTE: For the red flash threshold, a flash is defined as any pair of opposing transitions to or from a saturated red at any luminance level . (See note below)

NOTE: Thresholds are based on ITC Guidance Note for Licensees on Flashing Images and Regular Patterns in Television (Revised and re-issued July 2001) as modified by the Wisconsin Computer Equivalence Algorithm.

marked in a way that the user can avoid its appearance

The content is marked in a fashion that would allow the user to determine that provocative material can be avoided. Some methods that might be used for this include:

• metadata on the page

• information in the title (so search engine shows it)

• notification on the page before provocative information is encountered.

Editorial Note: This definition needs work.