Use of the JDBC-ODBC bridge from an untrusted applet running in a browser, such as Netscape Navigator, isn't allowed. The JDBC-ODBC bridge doesn't allow untrusted code to call it for security reasons. This is good because it means that an untrusted applet that is downloaded by the browser can't circumvent Java security by calling ODBC. Remember that ODBC is native code, so once ODBC is called the Java programming language can't guarantee that a security violation won't occur. On the other hand, Pure Java JDBC drivers work well with applets. They are fully downloadable and do not require any client-side configuration.
Finally, we would like to note that it is possible to use the JDBC-ODBC bridge with applets that will be run in appletviewer since appletviewer assumes that applets are trusted. In general, it is dangerous to turn applet security off, but it may be appropriate in certain controlled situations, such as for applets that will only be used in a secure intranet environment. Remember to exercise caution if you choose this option, and use an all-Java JDBC driver whenever possible to avoid security problems.