Can you have a different skin to forum skin on portal?

[Diana]

Weird question and I think I know the answer, but is it possbile to have a different skin on your portal? And then another skin for the forum itself?

I don´t know anything about the html homepage so I cannot do that. Is it possible with just the portal? If the HTML is the only way can you give me tip by tip explanation, cause I really don´t understand the tutorial thingy I saw here.
What I want to do is change the portal according to holidays and special dates but leave the forum the same.