I was reading this webpage, not sure if webpage is the correct term, and saw that it has a minus sign for the potential 12 describing how the two electrons in a helium atom interact with each other. Although this was opposite of what I would have expected I initially considered that if the writers of a webpage put something unexpected in an equation, then it is much more likely that it's because I have a blindspot in my understanding than that the writers actually made a mistake.
However the minus sign made me suspicious enough to look at other sites to see if they also had the minus sign, as I realized that if they made a mistake then the other sites would most likely have a plus sign in for the potential 12, while if having a minus sign being unexpected for me came from a blind spot in my understanding then they would most likely also have a minus sign for the potential for how the electrons interact with each other.
I found that this site, this site, this site, and this site all have a plus sign for the interaction potential describing the interaction between the electrons, and these are .edu sites, with some of them being pdfs so now it looks like the original site I looked at has something that contradicts multiple academic sites and so it's more likely that the writers of the site I originally looked at did make a careless mistake in the equation. Note that one of the other sites initially looks like it has a minus sign for the potential I described, but that minus sign is canceled out by another minus sign.
The question now is what is the best way to let the writers of the webpage know that they made a mistake? I saw the contact information, so I know how to contact them, but I don't know the best way to tell them that they made a careless mistake.