Issue with Altervistia Host

Hi, I am wondering if you could help. I have been trying to get some error messages fixed which have been on my wordpress website i contacted the theme authors regarding the issue and they seem to think its an issue reffering to the hosting server. The details for the host account is as follows:- Server: ftp.rachelleandbrittany.altervista.org
If you get following error "Warning: getimagesize(): http:// wrapper is disabled in the server configuration by allow_url_fopen=0...

Please contact your hosting service, and present them the errors, and they should be able to resolve this for you.

Also note that since these are Warnings, not errors, they are not harmful for your site, and you can also hide these messages by disabling wp_debug https://codex.wordpress.org/WP_DEBUG and by contacting your host and asking them to disable Warnings display. I am wondering could you fix this or even disable warning messages. Thanks for your help on this matter.

That code is doing something really stupid: it would perform a full HTTP request to only get the size of an image on your own webspace.
It looks something related to the slider and shortcode. How did you setup the slider?