Clicked on a USERS website in profile and got an ERROR

[jimmyc2018]

One of my users added a website to their profile, when I clicked on it - it didn't open in a new tab like I imagined instead I got this ERROR:

ON PAGE:
Not Found
You seem to have stumbled upon a page that does not exist. Return to the home page.

ADDRESS BAR:
https://www.MyForum.com/user/http;//www.UserWebsite.nl

What do you think happened?

[PitaJ]

It has a semicolon and not a colon, so the browser interpreted it as a relative path.