In common dialogs, the vertical alignment of the text relative to the icon (on Windows, I didn't look at Linux) has changed between Fx3.6 and the 2010-10-30 nightly. Looking at several other popups from other apps and from Windows itself, it seems like the convention is to more-or-less align the top of the text with the top of the icon. It was that way for Fx3.6, but it's lower now for Fx4. Seems like a regression. This looks like it has to do with hiding the title (Bug 563274, Bug 575485) on platforms other than Mac. Maybe also hide the spacer whenever the title is hidden? Screenshot coming.
Nominating for blocking, because I'm not sure how important a bug this is considered in UI-land...
Just to amplify a little: The dialogs at issue are the ones shown with window.alert(), window.prompt(), and window.confirm(), i.e., the ones represented by commonDialog.xul. STR is just window.alert('your text here'), and compare the result on 3.6 vs. a trunk nightly. The title mentioned above is <description id="info.title"> in commonDialog.xul, and the spacer is the element right after it. The in-dialog title is there because on the Mac there's no title above the dialog (no windowframe, no titlebar), so it's shown inside the dialog itself -- but only on the Mac. The spacer is there to separate the text of the in-dialog title (when that is shown) from the text that follows it. When the in-dialog title is hidden, the spacer should be hidden too (I think), else you get the extra vertical space. http://mxr.mozilla.org/mozilla-central/source/toolkit/components/prompts/content/commonDialog.xul#60 CCing Dolske because he worked on Bug 575485. I don't know how much this matters either, but the icon does seem to stick out a little now.
Not blocking, but a polish nit we should fix. Will pick this up, perhaps in the course of something else.
Created attachment 503092 [details] [diff] [review] Patch v.1 Trivial fix.