How to disable url function in button

Hi,
I need to disable url function in button. As you can see in the link, when you click on the button, a drop-down form opens and ask user to insert his/her info. However, the issue is , even though I’ve deleted url section while inserting button, it stills redirect users to the home page..
I tried inserting # in urls section or button id, non worked properly. The following javascript function did abit what I want , however, it still is far away from what I exactly looking for since it cuases the page to jump to the form.
onclick="function reveal(e) {e.preventDefault()}

Any idea how to slove the issue?
Thanks in advance.

The page I need help with: [log in to see the link]