Javascript on IE/Firefox

We have a Gregorian calendar in Report Studio. We have 2 browsers: IE and Firefox. You have one browser where you have to click the checkbox on the calendar to make it work, the other browser, where you don’t to get the calendar to work the same way. We have the following HTML code before and after the calendar.

Any ideas on how to get consistency in this? In other words, if the user wants to select the calendar prompts, they check it. If the user doesn’t want to select the calendar prompt, they leave it unchecked.