Comment by no_gravity

Interesting. And to render the html you can use cutycapt. Which is in the Debian repos too. I just tried it, and this rendered a nice diff of two pages for me:

  cutycapt --url=http://www.xyz.com/1 --out=1.png
  cutycapt --url=http://www.xyz.com/2 --out=2.png
  compare 1.png 2.png diff.png