on the page <a href="http://www.yvon-thoraval.com/CSS/footer_long.html">overflow:auto block the vertical scroller</a> this css is only effective on the div #content.
then, no way to scroll up and down the content of a page whose content is larger than the window height.
obviously this doesn't appear if the content of the page is smaller than the window height, a counter example being here :
no need of a vertical scroller at all.
I have encountered the same problem. However this does occur for overflow:scroll as Well. Further the horizontal scrollbar doesn't work either.
I would suggest to change the title to something like:
"overflow:auto and overflow:scroll block the vertical and horizontal scroller"
Created attachment 11677 [details]
attached testcase. Just try to use the scroolbars with WebKit nightly. It is not working.
*** This bug has been marked as a duplicate of 11632 ***