Itunes cannot read Korean letters, instead I get these letters (¿À´Ãµû¶ó º¸°í½Í¾î¼­ ±×·¡)

I downloaded several Korean songs from a website. Then I synced all the songs into Itunes, but some of the Korean songs are visualized with these letters instead (¿À´Ãµû¶ó º¸°í½Í¾î¼ ±×·¡). I have no idea what this is. Please help. Additionally, only some of these songs are titled with those weird letters.