Problem description

When trying to launch MineCraft on the web at https://minecraft.net/classic/play you get the following error: black screen displaying message "Switching applet":

Reasons explained:

• MineCraft Classic is an old MineCraft version which is not maintained anymore and won't run with recent Java RunTime Environment versions. For instance, Jre 7 update 45 is not compatible with MineCraft Classic and will never be ;(.
• In fact your are stucked during the launch process for security reasons due to the too recent version of your Java RunTime Environment ...

Workaround

Summary

You need to "downgrade" your Java version. See below a step by step guide.

Detailled step by step procedure

• Go to http://www.oracle.com/technetwork/java/javase/downloads/jre6downloads-1902815.html and download the suitable jre package for your OS. I suggest to install jre 6 (for instance to install and run Java under Windows XP / 32 bits, choose : jre-6u45-windows-i586.exe). It seems that somme "old" jre 7 versions are also working: for instance jre 7 Update 9 is also fine
• During the download, remove the previous Java installed (if any) on your computer
• When Java download is completed, install the "old" Java version and ... MineCraft should now work online.

Pay attention not to accept the upgrade proposed at each Java launch  or you will have to perform the previous task again: remove recent / re-install old JRE version.