As you might know, SharePoint's Web browser support is divided into two levels: level 1 and level 2.

• Level 1 Web browsers take advantage of advanced features provided by ActiveX controls and provide the most complete user experience. Level 1 browsers offer full functionality on all SharePoint sites, including the SharePoint Central Administration Web site.
• Level 2 Web browsers provide basic functionality so that users can both read and write in SharePoint sites and perform site administration. However, ActiveX controls are supported only in level 1 browsers. In addition, there are functionality differences between different browsers.

After the release of Service Pack 2 for SharePoint 2007, there has been updates to list of Level 1 and Level 2 browsers supported. Given below is the updated list. 

Level 1 Web browsers for SharePoint 2007 with SP2 are:

• Windows Internet Explorer 6.x (32-bit)
• Windows Internet Explorer 7.x (32-bit)
• Windows Internet Explorer 8.x (32-bit) (includes running in compatibility mode)

Level 2 Web browsers for SharePoint 2007 with SP2 are:

Please refer to the updated article in TechNet - Plan browser support for the latest support information.