Firefox 3.5.6 works in Expression Web 3 SuperPreview
The Expression Web Team blog blogged last month about a Firefox bug their customers encountered using SuperPreview with Firefox version 3.5.5. With the newest release of Firefox 3.5.6, the Mozilla team has fixed the bug. They recommend that you update to this latest version of Firefox 3.5 to use it again in SuperPreview.
More at: Expression Web team blog