CSS placeholder not working when comma separated

Question

When working with styling placeholders, why is this working

#search::-webkit-input-placeholder {
   color: red;
}

#search:-moz-placeholder {
   color: red;  
}

#search::-moz-placeholder {
   color: red;  
}

#search:-ms-input-placeholder {  
   color: red;  
}

While this is not?

#search::-webkit-input-placeholder,
#search:-moz-placeholder,
#search::-moz-placeholder,
#search:-ms-input-placeholder {
    color: red;
}

Isn't that the second snippet is just to group them together? Is there a special case for this?