Most hotel wifi networks require opening a browser to connect. Once you open it, the first page you go to is redirected. Because a lot of sites default to HTTPS, that redirect is detected as a MITM by the browser, and prevents you from moving on. http://neverssl.com/ is an easy way to get to the portal without an issue.
As noted on NeverSSL:
> [...] it [...] means that if you're relying on poorly-behaved wifi networks, it can be hard to get online. Secure browsers and websites using https make it impossible for those wifi networks to send you to a login or payment page. Basically, those networks can't tap into your connection just like attackers can't. Modern browsers are so good that they can remember when a website supports encryption and even if you type in the website name, they'll use https.
All the other replies to your comment are "this is a permanent solution to the problem"; but I think to truly answer the spirit of your question, the correct answer is "yahoo.com": I mean... can you imagine Yahoo! ever getting around to adding SSL to their website? ;P
I use ipchicken.com, works over http for public wifi signins, and has added benefit of showing me whether I’m connected to wifi/4g/vpn via IP’s reverse DNS.
Redirects are fine as long as they aren't HSTS preloaded - you can open it in an incognito window if your browser has cached the redirect.
I usually use gstatic.com, which does redirect, but also gstatic.com/generate_204 is Chrome's own capive portal test page and does not redirect. There's also msftncsi.com, which (/ncsi.txt) is Microsoft's test page.
And, despite money.cnn.com being one of the Subject Alt Names on their certificate (as well as plenty of app, api and some staging domain names), that domain in particular rejects connections to port 443.
Maybe their transition is incomplete and they're not ready to announce yet?
I've been seeing it for six months almost. Maybe https-everywhere was doing this but I also used to use CNN as a hotel WiFi sign-in gate so I noticed it back then.
Funny how many people independently ended up in that same situation. How did y'all start?