It really heated up the web browsers' war, when Mozilla joined the European Commission's antitrust case against Microsoft, throwing its support behind the European Commission.

In its antitrust case against Microsoft, the European Commission accused the Redmond, Washington based software giant of illegally attaching its Internet Explorer browser to its Windows operating system.

Mozilla, which has been granted the status of "interested third party" in the case, can submit arguments to the European Commission against Microsoft and can take part in a face-to-face hearing if Microsoft asks for one. However, Mozilla is a complainant in the case; the complainant in the case is Norwegian Web browser Opera that lodged a complaint with the EC, against the Microsoft's practice.

"There isn't the single smallest iota of doubt that Microsoft's tying of IE to Windows, and the tying harms competition between web browsers, undermines product innovation and ultimately reduces consumer choice," Mitchell Baker, Mozilla Corporation's chief executive, wrote in her blog.

"I'll be paying close attention to the European Commission's activities, both personally and on behalf of Mozilla. I'd like to offer Mozilla's expertise as a resource to the commission as it considers what an effective remedy would entail," Baker added.

Mozilla's joining the case as "interested third party" is viewed as the significant development, as it is a chief competitor of Microsoft in the web browser market. According to the French researcher XiTiMonitor, Firefox is Internet Explorer's nearest rival in Europe.