In Exclamation marks^x, Vocabulary^x

I don't really know where to post this. It's not a grammar question nether a vocabulary in my opinion.. Well, should we use a capital letter after a question mark or an exclamation mark? This question came to my mind in a sudden when I was writing a post... ...I know, I know..it's a stupid...

Easy! Just write something and post it here. Someone will help you correct it. For example: "Hello, everyone. My name is Ann. I've just graduated from university and am hunting for a job now. Someone said that my oral English is quite good, but my written English is vefy poor. I dont know how...