Sorry for the inconvenience. Whatsapp web requires the using browser's UserAgent exactly the same with the listed 4 browsers.
Unfortunately we added our own UserAgent flag in version 1.4.0.2. So it is not allowed to access Whatsapp web.
As a temporary solution, you can use an extension to do UserAgent spoof.
https://chrome.google.com/webstore/detai...pkjnoahfmg
After installed, go to its options and select "Custom User-Agents", and add a custom UserAgent.
Fill "New User-Agent String" area with "Mozilla/5.0 (Windows NT 6.3; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/44.0.2403.157 Safari/537.36".
Then select this new UserAgent as default and now you can access Whatsapp web.
Later we will add an option to allow our users hide our own UserAgent flag.