Element

img

Error Type

Potential

Guidelines

  • BITV 1.0 (Level 2)
    Guideline GroupLevel 1
    Guideline Subgroup7.1 Until user agents allow users to control flickering, avoid causing the screen to flicker.
  • Section 508
    Guideline GroupJ - avoid flicker
  • Stanca Act
    Guideline GroupRequirement 5: Flicker
  • Visual Content
    Guideline Group[ _GROUPNAME_90 ]
  • WCAG 1.0 (Level A)
    Guideline GroupPriority 1
    Guideline Subgroup7.1 Until user agents allow users to control flickering, avoid causing the screen to flicker.
  • WCAG 1.0 (Level AA)
    Guideline GroupPriority 1
    Guideline Subgroup7.1 Until user agents allow users to control flickering, avoid causing the screen to flicker.
  • WCAG 1.0 (Level AAA)
    Guideline GroupPriority 1
    Guideline Subgroup7.1 Until user agents allow users to control flickering, avoid causing the screen to flicker.
  • WCAG 2.0 (Level A)
    Guideline Group2.3 Seizures: Do not design content in a way that is known to cause seizures.
    Guideline SubgroupSuccess Criteria 2.3.1 Three Flashes or Below Threshold (A)
  • WCAG 2.0 (Level AA)
    Guideline Group2.3 Seizures: Do not design content in a way that is known to cause seizures.
    Guideline SubgroupSuccess Criteria 2.3.1 Three Flashes or Below Threshold (A)
  • WCAG 2.0 (Level AAA)
    Guideline Group2.3 Seizures: Do not design content in a way that is known to cause seizures.
    Guideline SubgroupSuccess Criteria 2.3.1 Three Flashes or Below Threshold (A)

Requirement

All img elements have associated images that do not flicker.

Error

Image (GIF) may flicker.

Short Description

This error is generated for all img elements that contain a src attribute value that ends with ".gif" (case insensitive). and have a width and height larger than 25.

Rationale

People with photosensitive epilepsy can have seizures triggered by flickering or flashing in the 4 to 59 flashes per second (Hertz) range with a peak sensitivity at 20 flashes per second as well as quick changes from dark to light (like strobe lights).

How To Determine

Question Does this image flicker?
PASS Image does not flicker.
FAIL Image does flicker.

Steps To Check

Procedure

1. Check each img element that has a src attribute value ending in '.gif'.
2. View the associated image and determine if it flickers using the general flash threshold and red flash threshold.

Expected Result

1. All img elements have associated images that do not flicker.

Failed Result

1. Use another image that does not flicker.

Examples

Pass Examples

Image does not flicker.
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/REC-html40/strict.dtd">
<html lang="en">
<head>
<title>ATRC Testfile - Check #10.2 - Negative</title>
</head>
<body>
<img src="rex.gif" alt="A brown and black cat named Rex."/>
</body>
</html>

Fail Examples

Image flickers.
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/REC-html40/strict.dtd">
<html lang="en">
<head>
<title>ATRC Testfile - Check #10.1 - Positive</title>
</head>
<body>
<img src="eatatjoes.gif" alt="eat at Joes" width="200" height="200"/>
</body>
</html>

English | German | Italiano


Web site engine's code is copyright © 2011
Inclusive Design Institute
Web Service API