“Unknown property” warning for every .css file and line in javafx

I had a similar issue and rectified it by ensuring I had included all of the JAR's and Libraries that I required in the Build Path. I had to add Joda Time JAR, SQLite Jar, SceneBuilder Jar and the JavaFX SDK Library.

It is also important to leave these files 'unticked' in the Order and Export section of the Java Build Path.

You should install e(fx)clipse

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I assume you have Web Tools Platform installed already.