Menu Column Bug Chrome/Firefox

Hello,

I have been building and testing my new WordPress site within Google Chrome and I have a question regarding web browsers. To my knowledge, my site should appear and look the same across all modern browsers but I’ve looked at the same pages on Chrome and Firefox and they look different.?

The Menu looks different on the latest version of Firefox in comparison to Chrome. Screenshot1 (https://bit.ly/2JamA5O) is how it is supposed to look and this is from Chrome. Screenshot2 (https://bit.ly/2FyJi6z) shows how the site looks on Firefox. What is causing this problem and can anyone help me fix it?

Thanks in advance,

Regards

calvintct

The page I need help with: [log in to see the link]