This README.md uses the markdown syntax available at [https://github.com/adam-p/markdown-here/wiki/Markdown-Cheatsheet]

Installation

Right before closing tag of the HTML page, call the JS script from cdn.jsdelivr.net, using the hashed version ebe361e: <script src="https://cdn.jsdelivr.net/gh/costincca/web-styles-debug-window@ebe361e/web-styles-debug-window.js"></script>

This is because Github's hotlinked version:

<script src="https://raw.githubusercontent.com/costincca/web-styles-debug-window/master/web-styles-debug-window.js"></script>

is restricted for running in the browsers, as Github implemented a X-Content-Type-Options: nosniff header to prevent executing files directly. For more information, please see: [https://stackoverflow.com/questions/17341122/link-and-execute-external-javascript-file-hosted-on-github].

If hashed version changes, the new version should be replaced in the URL:

Configuration

By default, even if it is installed in page, the script does not show anything. To bring up the debug pane, URL parameters need to be specified:
dbg

Values:
1 - brings up the full draggable debugging pane
2 - brings up the fixed semitransparent non-draggable debug panel on top of the content
3 - brings up the sticky opaque debug panel, sticky at the top of the page, on top of the content
4 - brings up the small opaque debug panel, not sticky, on top of the content, which shows only DPR, width and height values

dbgcol

Values:
number - shows the information on the specified number of columns (default: 2)

Example:

..../index.htm?dbg=1&dbgcol=4

Currently, only the following styles are displayed: 'H1', 'H2', 'H3', 'H4', 'H5', 'H6', 'P', 'A'. But the JS file can be downloaded from Github, edited the first line with the desired tags, then linked to this locally modified file.