Your browser reports that it doesn't support modern technologies - in this instance, WebP. This means you're most likely using Internet Explorer or Safari. You can carry on using the site if you really want to, but won't be able to see any images until you upgrade to a modern browser.
Waterfall's recommendation is Firefox - it's fast, secure, and does a good job at protecting your privacy.
For all my fellow artists, just found this really good free to use pose reference source, @kamitokatachi on twitter. Not only do they have a metric fuck ton of screenshots of posed semi-realistic 3d models, but each pose has various perspectives and lighting sources.