Created attachment 17036
Firefox 33

Cannot reproduce here with Firefox 33.
What's those custom tab names about? :)

Attached:

Commons found out that this is https://github.com/wikimedia/mediawiki-skins-Vector/commit/deac6028635ec8799299446a2a1f26f7d05b27ac#diff-ea4c71a38323ab185c591dde27f1c5c4L54.

/me loves GlobalCssJs :)

So wait, is there something broken in our code (I definitely did not intend the indicators change to push the title down), or was the issue caused by some custom on-wiki CSS?

From the IRC conversation: The move only happened on 1.25wmf6 wikis (tested on Commons, Meta; didn't happen on en.WP or de.WP), and your change I linked to is "responsible" for it. Quote zhuyifei1999: "FDMS4: there's "padding-top: 0.5em;" on "div#content h1" on commons, but enwiki used "padding: 0;" on ".mw-body h1" in https://bits.wikimedia.org/en.wikipedia.org/load.php?debug=true&lang=en&modules=skins.vector.styles&only=styles&skin=vector&*".

I thought your indicators require the extra space. As having read your comment I am no longer sure this is true, reopening.

Correction and expansion to my previous IRC comment:
In a css block (in previously unknown source) there is:

div#content h1,
div#content h2,
div#content h3,
div#content h4,
div#content h5,
div#content h6 {

line-height: inherit;
 margin: 0;
 padding-top: 0.5em;
 padding-bottom: 0.17em;

}

which sets "div#content h1" to have "padding-top: 0.5em" and "padding-bottom: 0.17em"

Another more specific css block in another unknown source (which I have not dug further), there is:

div#content #firstHeading {
font-size: 1.6em;
line-height: 1.2em;
margin-bottom: 0.1em;
padding-bottom: 0;
}

which resets "padding-bottom: 0"

Previously in module "skins.vector.styles" there was another specific css block:

.mw-body h1,
.mw-body h2,
.mw-body #firstHeading {

	  font-family: "Linux Libertine", Georgia, Times, serif;
	  line-height: 1.3;
	  margin-bottom: 0.25em;
	  padding: 0;

}

to reset all paddings to 0.
However, ".mw-body #firstHeading" was removed and ".mw-body h1" is not as specific as "div#content h1", so it's overridden by the first block to have a final "padding-top: 0.5em", which is shown as the blank space on the top of the title.

But further digging I just done shows that the first block comes from ext.gadget.typographyrefreshoverride (In this case for FDMS, it's his glocal css). So for anyone who doesn't use this override, this bug just doesn't show.
Thus there're two ways to fix this bug:

1. partly revert the git commit.
2. fix all the typographyrefreshoverride gadgets and user css.

Created attachment 17060
Firefox 31 (logged-out)

Also reproducible (by me and marktraceur) while logged-out (and therefore without TypoRefreshOverride) …

Attached:

(In reply to Stöger Florian D. M. from comment #6)

Created attachment 17060 [details]
Firefox 31 (logged-out)

Also reproducible (by me and marktraceur) while logged-out (and therefore
without TypoRefreshOverride) …

Confirmed from me as well for logged-out. Unconfirmed for logged-on without TypoRefreshOverride. Looks like there's something weird going on (I'll look into it tomorrow if necessary).

Attached:

(In reply to Stöger Florian D. M. from comment #6)

Created attachment 17060 [details]
Firefox 31 (logged-out)

Also reproducible (by me and marktraceur) while logged-out (and therefore
without TypoRefreshOverride) …

This is caused by

 	#localNotice {
		margin-bottom: 0.9em;

}

under module "mediawiki.skinning.interface"

[[:c:MediaWiki:Anonnotice]] has '<p style="display:none"></p>' which makes mediawiki and browser *think* there is a anonnotice above when there is none, leaving an empty space that is used to separate sitenotice with the page title.

Attached:

Indeed, appears to be fixed now – http://enwp.org/c:Special:Diff/155289645 …