I have just hit a small bug in Firefox3 that has a big impact on fullZoom. If you shrink a Firefox 3 window, the window's width does not shrink beyond the toolbar's minimal width.... It's bug 391358. It means that if you shrink the window to a 250px with, your viewport is still roughly 450px wide ! Your vertical scrollbar is hidden, your content is not centered any more in the window, and so on. See IE8, FF3 and Opera9 browsing www.lemonde.fr with a 20% zoom factor and all windows having 250px width:

screenshot

Until this is fixed, my new glazoom extension's feature "Fit horizontally in window" will not work correctly for small window widths.