Comment 5 for bug 1394725

To quote from the wiki page (by Inkscape's resident SVG expert):
«Absolute units (other than 'px' inside CSS) should not be used inside an SVG file with one exception:

The root width and height may have units, which with a proper viewBox determines an appropriate scale for a drawing. (This sets the "real" world value of the SVG user unit.) This reflect the opinion of the majority of the SVG working group.

In CSS a unit identifier must be present. As 'px' is defined in SVG to be the same as a user unit the following are equal: font-size="20" and style="font-size:20px". »