We're getting quite a few reports from people who can't go on the site due to an 'invalid' certificate.

It has to do with older systems / browsers that you use and will therefore also occur at other sites. We can't help this ourselves.

The only thing that helps is keeping your system / computer / browser / phone up to date and to download the latest versions.

These are the outdated systems that can suffer:
- Windows < XP SP3
- macOS < 10.12.1
- iOS < 10 (iPhone 5)
- Android < 7.1.1 
- Mozilla Firefox < 50
- ...

Check out your details here: https://www.whatsmybrowser.org