Hello,
If you have the font resizer enabled it can be changing the font style for the whole site. You can either disable or clear browser cache to reset it. Once you do one of these then you should be able to change it here:
body {
color: #191919;
font-size: 0.9em;
font-weight: 300;
letter-spacing: 0;
line-height: 193%;
}
template.css line 1