Page load times are similar, but while firefox and chrome render "instantly", IE takes quite some time (seconds)
There are a large number of controls on the page but we have replaced them with text boxes and its still much slower than other browsers and debugging is not helping. We use update panels and dynamic user controls for rendering but need better page analysis than the standard IE tools provide.
Its IE 10/11 and the original post was here:
https://social.technet.microsoft.com/Forums/ie/en-US/e96fcfea-7e59-4f67-ae02-9ac47aaa1527/ie-loads-page-under-2-seconds-then-rendering-takes-10-seconds-or-more-firefox-chrome-render?forum=ieitprocurrentver#e96fcfea-7e59-4f67-ae02-9ac47aaa1527
and move at suggestion