Browsers cache DNS which is separate from just clearing the cache which deletes temporary files.
To delete the DNS cache in Firefox follow these easy steps:
about:config into the address bar
- If you receive an acknowledge warning click next
- Find a option that is labeled
network.dnsCacheExpiration and set its value to
- Restart Firefox
In the event you could not find
network.dnsCacheExpiration simply create one and enter value 0, then after its updated you can put 3600 which I believe is the default.
You could opt to use the easy method of installing an extension, I use DNS Flusher which is available on the Firefox Extension Library, Simply enable toolbar at the bottom and click the IP address and it'll say FLUSHED. Then hit CTRL F5 or Mac Key F5.