What does this error mean when opening an svg icon sprite in a browser?

Question

Google Chrome

Answer 1

This means: XML has a non-standard (internal editorial) namespace "sketch:xxx" for which no URL is defined ( xmlns:sketch="http://example.com/sketch"or something like that).
If you are using an editor that works with these fields, the SVG is corrupted. If this is the result of some kind of "compilation" or "export" - remove these fields, the browser does not need them!