Site displays properly ONLY on Firefox!

The URL provided is not working at this time. Consult host

Your issue is CSS related (typically) so review this once site is up and running (If wrong URL was given please correct that):

To discover what CSS is output by your theme, use a web inspection tool such as Firebug: https://getfirebug.com/ , Chrome Inspect Element: https://developers.google.com/chrome-developer-tools/ or Internet Explorer 9+ F12 Dev. Tools: https://msdn.microsoft.com/en-us/library/dd565627(v=vs.85).aspx#csstool

There are others.

When editing CSS, use a Child Theme
https://codex.www.ads-software.com/Child_Themes
Custom CSS Plugin, or Theme provided custom CSS option.
Edits to parent themes are lost on theme update.

Learn CSS: https://www.w3schools.com/css/

Also make sure the change of CSS isn’t caused by a plugin. Disable all plugins, and check if the problem still presists.