Title tags change the formatting of my text

Hello,

I’d like to put H3 title tags in my table, but it changes automatically the formatting of my text (it’s blue, biggerfont,…). How can I keep the H3 title which is well reconized on my website and keep the formating I want?

I put in the CSS part :
h3 {
color: #FFFFFF;
font-size: 13px;
}

Is it the good way to do it?
Now it seems to work, but I’m wondering what is the name of the original font family? to have the same font everywhere.

Thank you,

Dan