What is the Toggle Ruler button?

The “Toggle Ruler” button located at the bottom of the HTML editor simply adds and removes a graphical pixel ruler along the outside of the design bed.

The ruler ticks are in 10 pixel increments in 100 pixel blocks. The ruler is used as a design reference for sizing elements on the page.

Clicking in the design body will set a red marker line at the corresponding width and height of the position in the design body.