Florida law defines a business pursuit as "a continuous and comprehensive activity for financial gain." State Farm Fire & Cas. Co. v. Friend, 478 So.2d 1198, 1200 (Fla. App. 1985). CMLP has identified no Florida cases interpreting this test in the context of online publishing out of the home (or elsewhere). The Friend case (above) suggests that a short-term, part-time activity carried out for money may not be considered a business pursuit when the primary motive of the activity is not financial gain (in that case, the insured person was helping out a friend).
Therefore, if you live in Florida, you may have an argument that your online publishing activities are not a "business pursuit" if your primary motivation is not financial gain. This argument might be undercut, however, if your publishing is more than a part-time, short-term activity.
Note that specific language in a policy might lead a court to a result different from the overall state trend.