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https://github.com/stowball/jQuery-rwdImageMaps (No longer maintained)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