Thanks for your hint. I'll add "english" flag.
This website is available in multiple languages. One can switch between the languages using the small flag icons at the top. But there's no British or American flag for English!
I tried to access the site from a Chinese computer, and it turned out to be quite difficult to switch it to English so I could navigate it. Looking at the URL, https://winscp.net/eng/docs/lang:chs , one would think that it's enough to replace chs by en, but this is not the case. What I needed to do is remove /lang:chs entirely.
I would like to suggest making it easier to switch the site to English by including a flag for it.