Internet Explorer 8 (abbreviated IE8) is the latest web browser developed by Microsoft in the long running Internet Explorer browser series. The browser was released on March 19, 2009 for Windows XP, Windows Server 2003, Windows Vista and Windows Server 2008. Both 32-bit and 64-bit builds are available. It is the successor to Internet Explorer 7, released in 2006, and is the browser included in Windows 7 and Windows Server 2008 R2. According to Microsoft, security, ease of use, and improvements in RSS, Cascading Style Sheets, and Ajax support were its priorities for Internet Explorer 8.