Most likely, Internet Explorer blocked the website because it's considered to distribute malware or to deceive you. However, if you think this is a false alarm, I recommend resetting the settings of the browser. Start Internet Explorer > Tools > Internet Options > Advanced > Reset. This could also be an add-on problem, but the Reset procedure should fix that as well.
Or the website might not be working at all and Internet Explorer can't display the page at that time.
