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Technique F58:Failure of Success Criterion 2.2.1 due to using server-side techniques to automatically redirect pages after a time-out

Applicability

  • Any server-side scripting language
  • Content does not meet the exceptions in the Success Criterion for permitted time limits.

This technique relates to 2.2.1: Timing Adjustable (Failure).

Description

Server-side scripting languages allow developers to set the non-standard HTTP header "Refresh" with a time-out (in seconds) and a URI to which the browser is redirected after the specified time-out. If the time interval is too short, people who are blind will not have enough time to make their screen readers read the page before the page refreshes unexpectedly and causes the screen reader to begin reading at the top. Sighted users may also be disoriented by the unexpected refresh.

The HTTP header that is set is Refresh: {time in seconds}; url={URI of new location}. It is also possible to omit the URI and obtain a periodically refreshing page, which causes the same problem. The HTTP header that is set is Refresh: {time in seconds}.

Examples

Example 1

The following example is a failure because a timed server-side redirect is implemented in Java Servlets or JavaServer Pages (JSP).

public void doGet (HttpServletRequest request, HttpServletResponse response)
      throws IOException, ServletException {
        response.setContentType("text/html");
	PrintWriter out = response.getWriter();
	response.setHeader("Refresh", "10; URL=TargetPage.html");
	out.println("<!DOCTYPE html PUBLIC \"-//W3C//DTD XHTML 1.0 Transitional//EN\"
	 \"https://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd\">");
	out.println("<html><head><title>Redirect</title></head><body>");
	out.println("<p>This page will redirect you in 10 seconds.</p>");
	out.println("</body></html>");
  }

Example 2

The following example is a failure because a timed server-side redirect is implemented in Active Server Pages (ASP) with VBScript.

 <% @Language = "VBScript" %>
 <% option explicit 
 Response.Clear
 Response.AddHeader "Refresh", "5; URL=TargetPage.htm"
 %><!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" 
 "https://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
 <html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en">
 …
 <!--HTML code for content that is shown before the redirect is triggered-->

Other sources

No endorsement implied.

Tests

Procedure

  1. Check to see if the web page automatically redirects to another page after some period of time without the user taking any action.
  2. Check if the page qualifies for Real-time or Essential Exceptions in Success Criterion 2.2.1 Timing Adjustable.
  3. Check if the user is provided an opportunity to turn off, extend, or adjust the timing of the page refresh.

Expected Results

  • If check #1 is true and checks #2-3 are false then this failure condition applies and content fails the Success Criterion.
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