Thanks Jason, unfortunately the php.ini cannot be altered as the website is hosted on a shared server. The hosting people advised me to precede the commands with "@" to stop the errors from displaying, but I have no idea which commands to apply this to - your advice would be appreciated.
Also, surely just preventing display of the error notices isn't going to fix the fact that the "browse server" function is not working? That's the real issue that needs to be resolved asap.
I have the latest version of design extender and so the fix of deleting "can-minify" from the script link doesn't apply.
The URL displayed after the page finishes loading the above error message is: mysite.co.nz/webassist/kfm/index.php?uicolor=%23eee&theme=webassist_v2&CKEditor=ContentValue&CKEditorFuncNum=1&langCode=en-gb
The page background goes grey.