Q:

W3C error on css

I am getting 2 error messages when I run my .css file through W3C and do not understand what is wrong. 
Does anyone have any suggestions.
Here is the error message:
117  img.floatright  Parse Error opacity=70)
79   Property -moz-border-radius is an unknown vendor extension

Corresponding line on my .css are:
 79:   -moz-border-radius: 10px 10px 0px 0px;
117:  filter:alpha(opacity=70);

A:

Properties starting with - are vendor prefix properties. They are used to experimental features which might become standard (without the -moz-, -webkit-, etc) in the future. They are not valid. border-radius has become standard and Firefox no longer supports -moz-border-radius as it has moved to the standard.
filter is a proprietary extension to CSS invented by Microsoft and used in older versions of Internet Explorer. It is not valid.

