д versus g

[wolfie-18.livejournal.com]

Is there ever any rule as to when to use д over g? I myself am used to writing g, but I was just wondering if there would ever be any situation in where a Russian would say "why are you writing it like that?" or "what???" When and where is д used more frequently? EDIT: That д (script) is actually supposed to look like an inverted б, but I don't know why it's not showing up.