Needs javascript to read... sigh.
View --> Page Style --> No Style
But as for the other complaint elsewhere in the comments, about light gray text, unfortunately Firefox can't help with that. Normally such misguided text is countered with Preferences --> Content --> Colors --> override ...
but in this case the gray is unfortunately in images and not text.And it gets even worse for the light gray text. OS X Accessibility has a setting to "Enhance Contrast". But in this case the gray is closer to white than to black, so all that "enhancing" does is make the text even lighter!
Sigh.
[1] https://cdn.rawgit.com/andreacorbellini/ecc/0939921/interact...