You can’t. You can, however tell if a particular URL is believed to be dangerous by any of several organizations that track such things.

Your browser probably has something built in; Firefox and Chrome do, for example. If you attempt to visit a known-bad URL, the browser will warn you and make you click through the warning before you do. Some other comments in this thread suggest third-party services that will also do this, and may even attempt to check the content found at the URL for known malware.