A great first step would be to clear your browser's cache
and then restart it. More often than not, a quick clear-out resolves most issues.
If you're still having trouble, check the problems occur on another computer or in another web browser. If they don't, you might have a problem with your device. If that's the case, confirm your browser is up to date and it's not infected with malware.
Failing all advice above, or if the problems are occuring on other computers and in other browsers, please send us a bug report
with as as much detail as possible.