Whatsapp announces web access to your application (limited access) on 21st January 2015.
To connect your web browser to your WhatsApp client, simply open web.whatsapp.com in your Google Chrome browser. You will see a QR code --- scan the code inside of WhatsApp, and youre ready to go. You have now paired WhatsApp on your phone with the WhatsApp web client. Your phone needs to stay connected to the internet for our web client to work, and please make sure to install the latest version of WhatsApp on your phone. Unfortunately for now, we will not be able to provide web client to our iOS users due to Apple platform limitations.
Source: WhatsApp blog
To connect your web browser to your WhatsApp client, simply open web.whatsapp.com in your Google Chrome browser. You will see a QR code --- scan the code inside of WhatsApp, and youre ready to go. You have now paired WhatsApp on your phone with the WhatsApp web client. Your phone needs to stay connected to the internet for our web client to work, and please make sure to install the latest version of WhatsApp on your phone. Unfortunately for now, we will not be able to provide web client to our iOS users due to Apple platform limitations.
Source: WhatsApp blog