A second is little disappointing, but in fairness my lowly, single CPU, single core server with only 1 GB of RAM (a t2.micro server on AWS) was struggling a little with the load that Hacker News sent to it yesterday (16,000 page views in a day compared to about a third of that number for the whole month before that!). Plus the images on this page are a particularly big (because they are quite detailed so can't compress them more without losing that detail). So it was probably a bit slower than usual. At the minute everything is served from that one server (no CDN either at the mo - I really should stick it behind Cloudflare). It was a little play thing for me to test stuff out with, that became an occasional blog too on the side.

My question was more of a "WTF is Firefox doing in the ~700ms between when the HTML has finished a network transfer and before the .css file is requested?"

I just tried it today and things are, in general, much faster (presumably due to the reduced load), but there is still over 500ms between when the .html completes the download and the .css is queued for transfer.

[edit]

I just tried it in a private window and most of the delay disappears, so I suspect extensions.