I'm sorry Andre.  The High Contrast setting for MS Windows forces the 
background of SVG images to be black.  I do not know how to fix this 
other than turning off High Contrast.

I believe you are seeing a black sign on a black background.  I believe 
you color selection palettes are also all black.  Can you view other SVG 
images on the web?  What color is the background of this image?

You should be able to view a sign with a black background and a white 
line.  I created an example.  Please open these 2 links and tell me what 
you see in each one.

Should work for everybody:

Should only work with High Contrast: