Users who are running Microsoft Internet Explorer 6 or Windows Internet Explorer 7 on a Windows XP-based or Windows Vista-based computer cannot join a Microsoft Lync 2013 meeting by using Lync Web App. When users try to join the meeting, they receive a message that states that the browser is not supported.
However, users can use Lync Web App to join a Microsoft Lync Server 2010 meeting, as expected.
To resolve this issue for users who are running Internet Explorer 6 or Explorer 7 on a Windows XP-based or Windows Vista-based computer, install the cumulative update that is described in the following article in the Microsoft Knowledge Base:
2835435 Description of the cumulative update 5.0.8308.420 for Lync Server 2013, Web Components: July 2013 Note After users install this cumulative update, they are prompted to install Microsoft Lync Attendee when they try to join the meeting. If Lync Attendee is already installed, Internet Explorer should start Lync Attendee automatically.
For more information about operating system and browser combinations that are supported in Lync Server 2013, visit the following TechNet website: