I am getting two errors in w3 css validtor as

1. Value Error : font-family Property font-family doesn't exist in CSS level 2.1 but exists in [css1, css2, css3] : Helvetica
2. Property src doesn't exist : url('tl\_files/Helvetica.ttf') format("truetype" )

my css with these code is\

```
@font-face{font-family:Helvetica;src: url('tl_files/Helvetica.ttf') format("truetype");}

```

how can I rectify these errors?