I installed a jquery plug-in, with it’s own css file, but it seems that all the tables in my web site have taken on the same style as defined in the jquery plug-in css:
How will that help? It will still apply those styles to all tables. The solution, as @Gandalf has already said, is to give a class to the table which is being targeted, to distinguish it from other tables, and then use the class to target the styles.