Microsoft Internet Explorer 7, by default, is limited to two server connections at a time. Microsoft Internet Explorer might become unresponsive or have slow performance when coaches have multiple AJAX calls and basic HTTP traffic.
Diagnosing the problem
When you use Internet Explorer 7, a coach might render a blank page without a source or be very slow.
Resolving the problem
To resolve this issue, either remove the custom AJAX calls or increase the maximum number of connections Internet Explorer 7 allows per server. See the AJAX - Connectivity Enhancements in Windows Internet Explorer 8 article on the Microsoft MSDN site for information on how to resolve the issue by modifying registry settings. More recent browser versions of Microsoft Internet Explorer, Mozilla Firefox, and Google Chrome have a default maximum per server connection value of about 15. Changing the value to 15 is recommended.