Although there are no absolute rules when using fonts in a design project, it is advisable to use no more than three fonts. More than three causes confusion and a jumbled design mess.
The body of your project should remain consistent, always use the same font throughout. Select a different font for you headlines, and sub headlines. It's OK to use bold, italicised, and different font sizes for your headlines.
Your project's font should always be readable. It is alright to use a script or decorative font for your headlines. Verdana is good for web copy, and Times New Roman is a readable font that works well with print body copy.
I've seen many blogs that use script font for the body, and not only is it hard on the eyes it presents an unprofessional appearance. Remember, when it comes to design "less is more".