[Doitsu]

@stumped: I also got the same W3C CSS Validator error message with Sigil 0.9.8 and the following (valid) minimal CSS file.

p {
text-indent : 0em;
}

a {
text-decoration : none;
color : inherit;
}

There's either a problem with the W3C CSS Validator web site or the W3C changed the servlet API parameters.

Until this is sorted out try the following:

1. Visit the W3C CSS Validation Service website
2. Copy and paste your CSS code and click Check.