I got a tip about this firefox plugin the other day and it is one of these “nice to have” plugins.
It will show the IP address(es) of the current page in the status bar, the IP will be red if connecting over IPv4 and green if connecting over IPv6. Requires that you are ipv6 enabled on your computer/ISP.
It also allows querying custom information services by IP (right click) and hostname (left click), like whois, netcraft, etc. Additionally you can copy the IP address to the clipboard.
Here is how it looks like when browsing this site
download it here: https://addons.mozilla.org/en-US/firefox/addon/showip/