NetBeans. Disable error checking underline

Question

How to disable error checking in NetBeans 6.9.1? It is very annoying to have red line in the source code.

This is similar to NetBeans - Turn off - wavy red underlines -

Answer 1

I have no 6.9 at hands, but in 7.x (and believe so, for some time) go to Options->Editor->Hints-> and uncheck

[ ] CSS (all those rules together)
[ ] HTML Validator (ditto)

Did the trick for me, when working with proprietary template files, 'coincidentally' named .html ...