How can I tell if a website is safe for conference registration? I am registering for a conference in Canada but the payment link has a weird name like yizhifubj and the website is Chinese.
Is that normal? Are there any guidelines for determining if a registration website is “safe”?
You will not be able to get a definitive answer on this unless you contact the conference organisers.  Certainly the registration mechanism is - by modern western standards - backwards - and you are right to ring alarm bells and take extreme caution as it could well be a scam

That said, @GlenPierce answer is not the final word - and there are significant elements which indicate that the site itself is credible - these include 


The actual payment IS done over HTTPS, and the certificate ties in with the domain name.  Of-course, this does not mean much, except that the domain has not been compromised.
The domain names associated with the site have been registered many years
The site purports to relate to academic.net - and, indeed, when you go to the academic.net website, the payment system does, indeed link to this domain name.   It is also relevant that most of conferences they have listed are held in China. 
If you log onto the site, and change the meeting ID, it lists different headers for different ID's - that means that if the site has been hacked, its been hacked for a while, and there is a "non-trivial" amount of coding behind this - and yet Google have not flagged it as untrustworthy.


My inclination is to believe that this is more a case of incompetence then likely fraud (and this level of competency is not that uncommon in the parts of Asia I've been exposed to) - but I would still not register this site without confirmation from the organizer that it is legit.