you know, loading a page in an iframe can only be done if the webpage is set to allow this:
if you can't view a page in your iframe, just check the network response of this site and look for:

header -> x-frame-options - if it is listed then
if you see SAMEORIGIN page loads only in iframes on the same domain
if you see ALLOW-FROM (uri) page loads only in iframes on that specific URI
if you see DENY page will nowhere load in an iframe

for example, if you try to load this wrong page urlyou will get the google error page, because on this there is no x-frame-option.



but if you try to load the (real) google main page
you will see ........ [nothing] because there is the x-frame-option set to SAMEORIGIN


with the html tag you can enter a part of the text using html-tags instead of bbcode ,
so you can enter unusual setting, like individual color or font-stylings.

This is just a Demo html Block