Invalid syntax highlighting
is a syntax error. For Java, the syntax highlighting should be:
or, if you don't want syntax highlighting (strongly discouraged because you can edit your own settings to adjust what you see),
See here for more details.
If you don't want to see syntax highlighting, you can either adjust your shared CSS file to disable it, or possibly use a syntax highlighter toggle utility.
BTW, it is also considered good practice (and good manners) to include some kind of edit summary in the box at the bottom of the edit window when making any kind of changes to a page so others can more easily tell what has been done.