If you posted this from work, your IT people could potentially see that you've posted it despite the fact that you had to login and are using https.

In this case, since the content itself is public, using https only helps to identify you personally for a site to know that you have permission to post as you. Think of a reddit post, just because you've logged-in to post this question, doesn't mean that post isn't public. Note that there are many cases where your connection to a website may be secure with https, but does not require authentication to access. So no, don't worry about your IT department viewing your gmail unless you're giving them your password or using a third-party mail client like Outlook (or anything other than going to Gmail's website in the browser or on your phone). If you're on a site that uses SSL (meaning your connection to that site is encrypted as https rather than plain old http) they can only see that you've visited the page, and not the content displayed upon it (unless they also had access)*. The best trick is to look at the https in the beginning of a URL.

Rest assured that nobody is able to read your gmail directly (because it's secure) without your password, but again, they'll be able to know you logged into gmail. Your IT people can potentially see which sites you've visited and when (through your browser history and looking at network traffic/requests) as well as the page content itself on sites that don't have a secure connection.

How to look at google chrome history