If something on the site isn't behaving correctly -- a button doesn't work or a pop-up doesn't close -- there are a couple of things to try:
clear your browser cache: The cache is where your browser stores pieces of a website that don't change often, like images or style sheets. By storing them on your device, the page can be assembled faster. However, this sometimes creates problems if an out of date file is in the cache and its current version isn't pulled from the website. It is pretty easy to force the browser to re-download everything – this site has instructions for all major browsers: http://refreshyourcache.com/en/home/ . Here are some instructions for specific browsers, some from the developer and some from elsewhere:
try a different browser: if you're on Chrome, try Firefox, etc.
try a different computer or device
upgrade your browser to latest version: here is a list: Browse Happy
run browser in private or incognito mode: this disables browser extensions which sometimes cause problems.
Please start a ticket or email firstname.lastname@example.org if these don't work – if you're having problems, we want to hear about it!