Well, everyone who says that this is due to auto-completion or fields due to the row being a header is incorrect. See this script for evidence:
http://jsfiddle.net/w25j9L7o/26/
The master space is not displayed by the browser or CSS or anything else at the DOM / Browser level. This is a font. The glyph H has a built-in gasket around it, and the larger the font size, the more noticeable the indentation.
Even if you use negative fields to compensate:
The character itself is shifted, which includes empty space, so the empty space will also slide, affecting the layout. The visible character does not slip into empty space, the entire character (visible and invisible) is shifted to the left if you use CSS to fix it.
You will need to adjust this offset based on the font size or determine the base percentage so that the offset increases with any font set.
Or you can simply use a different font that does not have this characteristic.
source share