Gmail Monospace Font

gmail.monospace.coffee.js

css = """
div.Bk {
    font-family: DejaVu Sans Mono, Courier, Monospace !important;
}
textarea {
    font-family: DejaVu Sans Mono, Courier, Monospace !important;
}
td > div {
    font-family: DejaVu Sans Mono, Courier, Monospace !important;    
}
"""

try
    head = document.getElementsByTagName("head")[0]
    node = document.createElement "style"
    node.type = "text/css";
    node.appendChild document.createTextNode css
    head.appendChild node
catch err
    try
        console.log "Error applying GMail style: "
        console.log err
        console.log err.stack
    catch err
        # pass

gmail.monospace.user.js

// @name          Gmail/Google Groups Monospace
// @namespace     http://owns.ch
// @description   Make emails and textareas in Gmail/Google Groups monospace
// @author        Alen Mujezinovic
// @homepage      http://gist.github.com/1451672
// @match         https://mail.google.com/*
// @match         https://groups.google.com/*
// @run-at        document-start
(function() {
  var css, head, node;
  css = "div.Bk {\n    font-family: DejaVu Sans Mono, Courier, Monospace !important;\n}\ntextarea {\n    font-family: DejaVu Sans Mono, Courier, Monospace !important;\n}\ntd > div {\n    font-family: DejaVu Sans Mono, Courier, Monospace !important;    \n}";
  try {
    head = document.getElementsByTagName("head")[0];
    node = document.createElement("style");
    node.type = "text/css";
    node.appendChild(document.createTextNode(css));
    head.appendChild(node);
  } catch (err) {
    try {
      console.log("Error applying GMail style: ");
      console.log(err);
      console.log(err.stack);
    } catch (err) {

    }
  }
}).call(this);

To install, click on the raw link on the javascript file. Enjoy.

Thanks!

I have updated your script in this fork. Now it works on recent versions of Google Chrome.