Needs an update, not working at the moment. Rated 1 out of 5 stars

(I'd like to write a bug report instead of a review, but there's no contact info!)

This add-on uses the add-on toolbar as its *only* UI entry point; however, the add-on toolbar hasn't been a thing for quite some time :-( so there's no way to get to the add-on. It's a very nifty and useful idea, but it needs an update.

Rated 4 out of 5 stars

A very convenient tool!

Rated 4 out of 5 stars

A simple and useful add-on.

The add-on will appear in the add-on toolbar at the bottom of the Firefox window.

Add a vertical guide line by clicking the hash (#) symbol. Once you've added a vertical guide line, you can convert it to a horizontal guide line by right clicking it. Click and hold to drag the guide lines to their desired position.

Thanks to the developer(s)!

Very innovative add on Rated 4 out of 5 stars

I love the concept of this add-on because i can easily put grid lines on any website.I can then measure the distance with other add-ons.
Suggestion:
How about some horizontal line and extending with a measure tool?

thanks for you review

Horizontal lines you can get just with right click on line.
I thought about measure between lines, I think it would be useful thing.

Now I am trying to find easy solution for this. I hope, next update will have it)