I’ve been noticing this recently. Thought it was just people using some tool to generated or compress jpeg images that was somehow generating broken jpegs.
After looking deeply at two people’s sites today, it appears WebPageTest is having problems with correctly processing jpeg files.
http://www.webpagetest.org/result/150904_G3_E6F/2/details is an example.
Notice “Compress Images” shows N/A + clicking on this really does say N/A for both compression + progressive for all jpeg images.
This appears incorrect, as there are many jpeg images on this person’s site + looking at them with ImageMagick - identify -verbose - seems to indicate image structure is correct.
Unsure if this is the correct place to report this.
If not, let me know the correct place.
Thanks.