how to run greasemonkey script before the page content is displayed?

Question

I am writing a plug-in for Firefox and using greasemonkey script to do that (I compile the user script using this tool http://arantius.com/misc/greasemonkey/script-compiler)

Answer 1

In addition to the previous answers I've found a solution that works flawlessly, just like previous versions of Firefox & GreaseMonkey. First off, run-at must be set to the earliest moment, so document-start:

// @run-at      document-start

Because the DOM is probably not loaded yet, wait for the document to get a readyState of interactive:

document.onreadystatechange = function () {
    if (document.readyState === "interactive") {
       // Do something
    }
}

While Greasemonkey implements more or less the same with document-end, I've noticed that the technique above works faster. Using this has resolved all issues I had in Firefox with flashing / jumping screens on pages when the DOM changes kicked in and directly loads the page as intended with the userscript.