We all know that there are a lot of trolls on the internet and the internet can be like the wild west, where anything goes. That being said, there are actual limits to the types of conduct which are legal under Florida law. The line the legislature has drawn is at cyber-stalking. This charge requires the State to show a pattern of harassing behavior directed towards a single individual over a period of time. These are high burdens for the state to meet; a single mean tweet is insufficient. In-person stalking has similar requirements for online cyber-stalking. The behavior needs to be egregious and consistent and for no valid purpose. If there are no aggravating factors, then stalking is a first-degree misdemeanor punishable by up to 364 days in the county jail. Aggravating factors that turn stalking into a third-degree felony punishable by up to 5 years in the Florida Department of Corrections include: stalking which includes making a credible threat, stalking in violation of a court order (such as a domestic violence injunction, for example), or stalking of a minor.
The reason these burdens are so high is because the legislature was concerned about making illegal conduct which is arguably protected by the first amendment. For example, consistently tweeting at your elected representative could possibly be a crime or it could just be you exercising your right to express your opinions about policy issues of the day.