When validating my css I get a Parse Error [duplicate]

Question

This question already has answers here:

W3C Validator error: Parse Error opacity=60 (2 answers)

Closed 8 years ago.

I am not sure why I am getting these parse errors.

Error 1:

    Parse Error Opacity=0)

My CSS:

    .ui-helper-zfix { 
    width: 100%;
    height: 100%; 
    top: 0; 
    left: 0; 
    position: absolute; 
    opacity: 0; 
    filter:Alpha(Opacity=0); }

Error 2:

    Parse Error mask()

My CSS:

    .ui-datepicker-cover {
    position: absolute; 
    z-index: -1; 
    filter: mask(); 
    top: -4px; 
    left: -4px;

Any help would be appriciated.

Answer 1

According to this Mozilla document, neither mask() nor Alpha() are defined filter functions. Also, the article implies that filter support is still experimental, which may be why the w3c validator doesn't like it.

In my experience, the w3c validator is pretty good about explaining why things fail. Check for additional error or description messages.

For the alpha effect, you may try: filter: opacity(0%)

This other stackoverflow question has additional information.

Answer 2

The filter property is not standard, but a Microsoft addition. That is why CSS parsers throw you those errors.

On another note: Are you targetting really old versions of IE?