Yahoo introduced avatars to its Messenger service in April 2004, when it completely revamped the service to include more graphics and animation. However, users could only customise their avatars using Microsoft's Internet Explorer browser.
Late last year, Mozilla launched the full version of its Firefox browser, which has continued to make significant dents in IE's market share. In February, Yahoo openly showed its support for Firefox by launching a toolbar for the open source browser.
This was followed a month later by the company pledging to make avatars available to Firefox user but the company did not give any timescales.
It is still unclear exactly when Yahoo started fully supporting Firefox - the company has been unavailable for comment -- but it is believed that Yahoo has been gearing up to provide the service since it started beta testing the next version of Messenger, which includes a free PC to PC voice telephone tool.