The centre part of any business web template has to be kept for showing off products or services. In the centre if there is a place the products or service with little description the users can easily understand what type of business you are running or what they can get from your site. So it is necessary that the layouts give you scope to utilize the space for attracting your visitors cum customers.
Because newsletter templates are available in all variety of lengths and sizes, there is really no limit to the content that you could potentially write. Keep in mind, however, that you should probably keep down your word count to a level that people are comfortable reading. While you may think everything that you are spouting off is fascinating, it's helpful to first sit down and make an outline of what you want your main message to be, or what the major news is that you are trying to share.