java.io.IOException: Server returned HTTP response code: 500-Collection of common programming errors

I’m facing this problem with Java. I want to get some HTML informations from a URL. This code was working for so long, but suddenly, it stopped working.

When I access this URL using the browser, it opens with no problem.

The code:

URL site = new URL(this.url);
java.net.URLConnection yc = site.openConnection();
BufferedReader in = new BufferedReader(new InputStreamReader(yc.getInputStream()));
String inputLine;
String objetivo = "