Opening a website on iPad also opens other random websites
I tested that web site and nothing happened. Granted it was on Firefox and Mac High Sierra.

May I suggest in your case usually cleaning Safari history does the trick.

Here is what Apple says how to do that.


  Delete history, cache, and cookies
  
  Here's how to clear information from your device:
  
  To clear your history and cookies, go to Settings > Safari, and tap Clear History and Website Data. Clearing your history, cookies,
  and browsing data from Safari won't change your AutoFill information.
  To clear your cookies and keep your history, go to Settings > Safari > Advanced > Website Data, then tap Remove All Website Data.
  To visit sites without leaving a history, turn private browsing on or off. 
  
  When there's no history or website data to clear, the setting turns
  gray. The setting might also be gray if you have web content
  restrictions set up under Content &amp; Privacy Restrictions in Screen
  Time.