Page Ruler is an extension that enables you to draw an adjustable grid layout on any page. 

To work with this addon, please navigate to a webpage and then press the toolbar button once. Once the addon is active, the toolbar icon is blue. For the inactive state, the toolbar button is gray. You can change the grid position (X/Y), line color, size, order (z-index), and line width (in pixel unit) via the extension options page. Reloading the active tab or pressing the toolbar button again will remove the grid from the page.

To report bugs or request a new feature, please fill out the bug report form on the addon's homepage (https://mybrowseraddon.com/page-grid.html).