This question references dnd-spells.com, which is not an official WoTC and property and has even been temporarily shut down by them in the past.
What is the policy on these references?
The exception is if the site is basically a piracy database. Our stance is to not link to such sites:
When we encounter these sources, revise the post to reference an official source instead — we don't want to appear to support or endorse their existence. I recommend you assume that anyone reading owns the books they need, so a feature/section name combined with a book name and page number will often be enough, and an SRD link would be beneficial if available.
As for legitimate non-official sites you may link to and reference whatever you like.