Newer versions of Firefox grey out any text in the URL bar that isn't the domain of the site you're on. If this bugs you, you can turn it off with a simple
To make URLs appear as straight black text, just open up a new tab and type
about:config in the address bar. Promise Firefox you'll be careful, then search for the
browser.urlbar.formatting.enabled setting. Double-click on it to change it to "False", and close that tab. Your URLs should now appear without any of the grey text.