The "Copy Profile to all Stack Exchange network accounts" button on the profile "Edit" page appears as in the following screenshot, with Safari 5.1.1 on Mac OS X 10.7.2:
The background is only set in part of the button.
On Google Chrome 15.0.874.121, and Firefox 9 (for Mac OS X), the result is the same.
When I use the Safari's Web Inspector, this is what it reports for that button.
What I find curious is that both the "background-position-x" and "background-position-y" properties for the button are set to 50%.
The issue is only present in Seasoned Advice; in other SE sites the button is rendered correctly.
In the latter screenshot, where the style is closer enough to the one used on Seasoned Advice, Web Inspector shows the following styles being applied to the button. (The screenshot is also a link to the full image.)
In this case, both the "background-position-x" and "background-position-y" properties for the button are set to "initial." Another difference I note is that in Seasoned Advice the background is both a transparent color, and an image, while in Programmers the background for the button is just an image (the color inherited from another element is overridden).