I have an existing image map in a responsive html layout. Images scale according to browser size, but the image coordinates are obviously fixed pixel sizes. What options do I have to resize the image map coordinates?
For responsive image maps you will need to use a plugin:
https://github.com/stowball/jQuery-rwdImageMaps (No longer maintained)
Or
https://github.com/davidjbradshaw/imagemap-resizer
No major browsers understand percentage coordinates correctly, and all interpret percentage coordinates as pixel coordinates.
http://www.howtocreate.co.uk/tutorials/html/imagemaps
And also this page for testing whether browsers implement