Azvista website page will always translate non-secured website link (forcing from 'http' into 'https') when a registration form is involved. This is to keep the connection/session secure. Most Website pages that requests data/input from user, will have a secure site available (in https). Clicking on website/link which does not have a secure site, will result in participant seeing a notice of "untrusted certificate".
A way to avoid this is by using shorterner sites such as: bitly/goo.gl to shorten the URL:
1. The shorten link may look like this 'http://bit.ly/1J8ZEvj', change the 'http' into 'https' to 'https://bit.ly/1J8ZEvj
2. Add this link as a hyperlink to your Azavista page with the protocol 'https://'