comments on aria-hidden

I find the section on aria-hidden a bit confusing [1]:
<quote>
If a menu is only visible after some user action, the aria-hidden 
attribute should be set to true until the menu is presented and the 
aria-hidden attribute is removed, indicating that the menu is visible. 
This allows the assistive technology to properly skip hidden elements in 
the document.
It is recommended that authors key visibility of objects off this 
attribute, rather than change visibility and separately have to remember 
to update this property. CSS 2 provides a way to select on attribute 
values ([CSS], Section 5.8.1). The following CSS declaration makes content 
visible unless the aria-hidden attribute is true; scripts need only update 
the value of this attribute to change visibility:
</quote>

The first paragraph implies that I should actually add and remove the 
aria-hidden attribute rather than just changing the value from true to 
false.  Is this really the case?  Does it really matter if I just toggle 
the value using setAttribute("aria-hidden", newValue)  rather than doing 
setAttribute("aria-hidden", true); and removeAttribute("aria-hidden")? 

 But, to confuse matters,  the next paragraph instructs me to use CSS and 
only change the value.  This recommendation seems to conflict the first 
paragraph?  Although removing the attribute value itself should still 
trigger the CSS rule properly since aria-hidden will no longer equal true. 
  Also, I think it should be noted that not all user agents support this 
CSS 2 selection feature.  Yes, you could argue that those same user agents 
also don't support ARIA, but with or without ARIA I need my hide/show code 
to work in IE 7 and I'd rather not have to code it twice - once using 
scripting and again using CSS!

thanks,
-becky

[1] http://www.w3.org/WAI/PF/aria/#aria-hidden


Becky Gibson
Web Accessibility Architect
                                                       
IBM Emerging Internet Technologies
5 Technology Park Drive
Westford, MA 01886
Voice: 978 399-6101; t/l 333-6101
Email: gibsonb@us.ibm.com
blog: weba11y.com/blog