HTML is a somewhat unforgiving venue for trying to create mathematical equations.  How your equation appears will vary depending on the reader's browser, device, nd zoom settings.  In order to facilitate ease of reading, the following are considered best practices for formatting your equations and expressions.

Include White Space

White space is your friend.  Put spaces everywhere in your equations.  Instead of typing x+5, type x + 5. Instead of typing x=7, type x = 7. This is especially important once you start nesting mathematical expressions.  FR{1 + FR{1,2},3} will be far more readable than FR{1+FR{1,2},3}. 

Avoid Deep Nesting

While the Equation Formatter does an excellent job formatting nested functions, it is good to remember that every time you nest a function, the text inside the nest gets smaller. Thus, a function within a function within a function may be unreadable to people reading your page.

Use a Larger Font

If you are a Pro Member setting up equations from within the Pro Control Panel, you have access to styles named "large" and "extra large." These are included specifically for situations when you need to deeply nest functions in a mathematical expression.