So what exactly is an em? The em unit traces its origin to the em box as used in print typography. The actual spatial rendering of an em is dependent on the glyphs of the font used. As such there is naturally a great deal of variance. The "1 em" spatial representation of an upper case letter X of the Courier font will be decidedly different from the rendering of the same upper case letter X of the Verdana font. Though at first thought it may seem confusing it is not. An "em" unit or "1 em" displays at the default or "base" size for a rendered font glyph as contained within an HTML element where the default display is assigned by the user agent. Generally speaking, text styled with a font-size 1 em {font-size: 1em;} will display as if no size declarations were assigned. Font-size "1 em" headers, sub-headers, paragraphs and other user-agent display controlled elements will all render at the default user-agent-determined settings.

So what exactly is an em? The em unit traces its origin to the em box as used in print typography. The actual spatial rendering of an em is dependent on the glyphs of the font used. As such there is naturally a great deal of variance. The "1 em" spatial representation of an upper case letter X of the Courier font will be decidedly different from the rendering of the same upper case letter X of the Verdana font.

So what exactly is an em? The em unit traces its origin to the em box as used in print typography. The actual spatial rendering of an em is dependent on the glyphs of the font used. As such there is naturally a great deal of variance. The "1 em" spatial representation of an upper case letter X of the Courier font will be decidedly different from the rendering of the same upper case letter X of the Verdana font.

So what exactly is an em? The em unit traces its origin to the em box as used in print typography. The actual spatial rendering of an em is dependent on the glyphs of the font used. As such there is naturally a great deal of variance. The "1 em" spatial representation of an upper case letter X of the Courier font will be decidedly different from the rendering of the same upper case letter X of the Verdana font.

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