Why scss is not blowing up for wrong css value

Question

I am using scss with haml in my rails3 project. I mistakenly typed

zindex: 99999

instead of

z-index: 9999

SCSS did not blow up.

I thought one of the benefits of using haml/sass/scss was not invalid css values are not allowed.

Answer 1

Sass / SCSS don't enforce valid CSS properties, just valid syntax. Your zindex: 9999 is still a valid syntax, but not a recognized CSS property.

CSS itself allows things such as custom browser extensions such as -moz-whatever that other browsers don't recognize. It would be too restrictive and impossible to maintain a list of up-to-date properties for Sass to filter.