Hiding Header Title Text

This comes dirctly from the WP documents on editing themes

“To hide the header text while leaving it in the code, do not change anything in your template files. Only change the CSS. Add display:none to the CSS selectors you do not want to appear. For example, to hide the text within the h1 selector:

h1 {display:none; font-size: 230%; color: blue;…….”

However I don’t know which CSS to change. I assume it is style.css in the TIGA theme, but when I added the dispaly none to the header section it does nothing. I also don’t see any h1 tag. Can somebody be more specific on WHICH CSS to change?

Here is a link to see what I am getting now

http://www.nevis1.com/nevis1blog/

Thanks