You can add custom text styling within cells by either Markdown or HTML. Markdown is a shorthand writing technique for HTML. It allows you to quickly and easily turn plain text into rich HTML. For example, simply entering
**bold text** would show up on your published site as bold text. To make formatting changes, open your spreadsheet in either Google, or your local spreadsheet application and then add the desired HTML or Markdown styling to your cells. Once saved and brought into Grid Iron 3, the results will only show on your published page (not in the Preview). A great formatting reference is available here.