When using the Find/Replace feature in Internet Explorer (10 and 11) and I click the Cancel button on the dialog, the following message is displayed:
"The webpage you are viewing is trying to close the tab. Do you want to close this tab?"
If I chose NO, then the Find/Replace dialog stays open. If I choose YES, then my entire tab is closed, causing me to lose any work I was doing on screen.
If you click the X button on the Find/Replace dialog, then the dialog closes without any prompts.
This also happens using your online demo at http://cutesoft.net/asp/EnableAll.asp