Using firefox on ubuntu

Here's the address on the page when I get the 'this connection is untrusted' message:

https://get.geo.opera.com.global.prod.fastly.net/pub/opera-developer/29.0.1795.14/linux/opera-developer_29.0.1795.14_amd64.deb

Would love to try Opera developer but cannot establish a secure connection

May be preventing many others from trusting the download

Thanks

bbjb