Assuming that you want the user to see the • you can simply escape that sequence, to give:
.down:before{
content:"\• ";
color:#f00;
}
As to why it's not visible on IE7, that's because IE doesn't support generated content or the :before selector.
Edited to offer that, to see the actual bullet character, you should use:
.down:before{
content:"\2022";
color:#f00;
}
JS Fiddle demo.