glines is a simple tool for easy markup testing with Photoshop-like guides. It adds Photoshop-like guides to the page that makes the alignment of blocks easier.

This tool is very easy to use: just add lines with the cursor to the page and move them around with the mouse or keyboard arrows. The lines can be deleted by double-clicking on them or by using the menu. You can also use some of the predefined ones.

The main advantage of this tool is that it helps you to learn the basics of HTML and CSS without having to download a single thing.