nb 6 daily build latest, on Mac OSX:

for:

.leftSidebar {
  float: left; 
  width: 180px;
  height: 250px;
  border: 1px solid #000000;
}

the visual editor does not show the settings in Border tab (bug 1 ? I guess border: 1px solid #000000; is a valid
setting), and then If I select Border...Top...Solid combobox entry, the correct border-top-style:solid entry is added,
but If I select <Not Set> in the combo box, I see this <not Set> entry in the css file, and then there is a NPE:
java.lang.NullPointerException
	at org.netbeans.modules.css.model.CssModel.updateModel(CssModel.java:286)
	at org.netbeans.modules.css.model.CssModel.access$000(CssModel.java:57)
	at org.netbeans.modules.css.model.CssModel$1.evaluated(CssModel.java:134)
	at org.netbeans.modules.css.model.CssModel$CssModelASTEvaluator.afterEvaluation(CssModel.java:317)
	at org.netbeans.modules.languages.ParserManagerImpl.setChange(ParserManagerImpl.java:174)
	at org.netbeans.modules.languages.ParserManagerImpl.parseAST(ParserManagerImpl.java:231)
	at org.netbeans.modules.languages.ParserManagerImpl.access$100(ParserManagerImpl.java:59)
	at org.netbeans.modules.languages.ParserManagerImpl$1.run(ParserManagerImpl.java:145)
	at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:539)
[catch] at org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:964)