Apologies if someone already answered this (threading on this listserv seems to be a little wonky), but I believe that 'Sans' is not a font, but instead a *font class*. SVG, despite it being the basis of the format for the desktop application Inkscape, is a web technology (the standard is maintained by the World Wide Web Consortium). In HTML pages (or usually, an associated style sheet [CSS]) that specify a font, you will often see them recommend a list ordered by priority of fonts that the browser should use for the indicated text. For body copy, it is often a sequence like Georgia, Futura, Verdana, serif. That tells the browser to use Georgia if it is available, and if not to use the next font in line. If no named fonts are available, it tells it to use any serif font it knows about.

Now, perhaps your system is not properly set up to register what 'category' the fonts on your system fall into (most fonts have metadata for this), so it is not available to Inkscape (or, presumably, the browser).

However, this is the limit of my technical knowledge about this issue, so I can only wish you luck and note that on my machine, the 'Sans' entry in the fonts dropdown does *not* have a little error indicator.

Hope this helps, -Arlo James Barnes