Best method for creating a universal extention/plugin

I'm looking to create an extension for the leading browsers (firefox, safari and ie). Its rather simple, and I'm looking for the most efficient way to go about this.

I need to get the hostname of the current site the user is on, and if it matches a certain parameter(eg, mysite.org), I'll need to append to the link some extra data and refresh to the new link.

What is 开发者_JAVA技巧the simplest way to go about this? (I don't want to go in the direction of a bookmarklet - since this would require the user to click. I'd like this to happen automatically)

sort of something like this:

if(window.location.hostname == 'mysite.org')
{
     location.replace(document.location.href + '/&mystuff=xyz');
}

Thanks!

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http://arantius.com/misc/greasemonkey/script-compiler