Barbara is only six years older than I, but in terms of the influence she’s had on my life she might as well have been my mother. She was an honors student in high school and studied Spanish for five years. As a thirteen year old, I often went with her to a special program run by our church that helped Hispanic immigrants learn to speak English. I watched Barbara take a deep interest in the lives of many of the people there. Sometimes she would bring me home, only to go back and spend additional hours helping old and young alike with their personal problems. By example, Barbara taught me not only the value of helping others, but the importance of loyalty and commitment.
So that authors can exploit the forward-compatible parsing rules to assign fallback values, CSS renderers must treat as invalid (and ignore as appropriate ) any at-rules, properties, property values, keywords, and other syntactic constructs for which they have no usable level of support . In particular, user agents must not selectively ignore unsupported property values and honor supported values in a single multi-value property declaration: if any value is considered invalid (as unsupported values must be), CSS requires that the entire declaration be ignored.