I often work with this add-on. It’s first class because it brings what I need. Runs technically flawless.

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A really handy addition allowing for improved design of web pages.

This extension is absolutely invaluable. It helps me figure out so many elements on a screen as I design websites.

Perfeito. Facilita demais o meu trabalho.

Good. it definitely does what it proposes. But it should have a percentage option. Percentage relative to the window in width and height.