Not knowing what you hope to achive, it's difficult to help. But HTML isn't for "cool effects" anyway, it's for describing document stucture and content. Use styles and scipting for "cool effects"
In the case of comment boxes, that has even less to do with HTML and everything to do with either server-side scripting or third party services.
For future reference: Your thread title isn't very practical, try to give desciptive thread titles.