In February 2008, Microsoft sent out private invitations for IE8 Beta 1, and on March 5, 2008, released Beta 1 to the general public, although with a focus on web developers.

IE8 development started in or before March 2006. According to Microsoft, security, ease of use, and improvements in RSS, CSS, and Ajax support were its priorities for IE8. Additionally, it introduced a Compatibility Ciew mode to optionally emulate older versions' rendering behaviour, and colour-coded tab groups where links opened in new tabs share the colour of which they originated from. Internet Explorer 8 is the first version of IE to pass the Acid2 test, and the last of the major browsers to do so (In the later Acid3 Test, it only scores 24/100). It was the default browser in Windows 7 and Windows Server 2008 R2. It was released by Microsoft on March 19, 2009, as the successor to Internet Explorer 7. Windows Internet Explorer 8 ( IE8) is the eighth, and by now, discontinued version of the Internet Explorer web browser for Windows.

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