It only means that your login does not go through a "secure" connection, unlike, for example, your email.
It means that someone could intercept your login details, but that would be highly unlikely to happen on a forum such as this unless you are stupid enough to use the same login details/passwords on multiple sites as that's when such details become useful.
I wouldn't worry about it, but I would be more worried about your claim that because you don't use Windows, I'm guessing you're on a Mac since you use Safari, you don't have to worry about viruses. Well, I have news for you, there is Mac malware, meaning viruses, trojans and other programs which exploit the usual backdoors left in the OS even after updating (or are created by the updates), they do exist and the numbers are rising as more people turn to Apple products. The numbers are not as high as with Windows, but they are out in the wild. It will do you no harm to ensure you have malware protection on your, what I assume, Mac.
I mean, I run Linux Mint and I still make sure there's AV protection despite it being more secure than either Apple or Microsoft products, better to be safe than sorry.