I use myetherwallet and I have no problems with it. As long as you do not share your private key to anyone else or any access for that matter then your coins are safe. You should always be careful when accessing some sites because there are times when you thought it is the legit site that you are accessing and it turns out that it's a phishing site and you end up losing all your coins. Being careful when accessing the sites is the way so that you can manage the risk like always accessing the site through bookmark and not just search it in google.