In CSS, unlike in jQuery, :not()
doesn't accept a comma-separated list of selectors. The parse error is probably a result of the validator trying to split the entire selector by that comma, which obviously won't work.
For your CSS to work you need to chain two :not()
selectors instead:
content form :not(#inp_submit):not(select) {
padding-top: 3px;
}
(Also, just as a sanity check, are you sure your content
selector is correct? It's a valid type selector, but there is no content
element in HTML.)