a {text-decoration: none;}
<link href='http://fonts.googleapis.com/css?family=Istok+Web:400,700' rel='stylesheet' type='text/css'>
font-weight: 400; #もしくは700
<style>
a {text-decoration: none;}
.gfont10 {font-family: 'Istok Web', sans-serif; color: #550000; font-size: 10pt; font-weight:700;}
.gfont10a {font-family: 'Istok Web', sans-serif; color: #550000; font-size: 10pt;}
.gfont12 {font-family: 'Istok Web', sans-serif; color: #550000; font-size: 12pt;}
.gfont12a {font-family: 'Istok Web', sans-serif; color: #808080; font-size: 12pt;}
.gfont12ab {font-family: 'Istok Web', sans-serif; color: #808080; font-size: 12pt; font-weight:700;}
.gfont12c {font-family: 'Istok Web', sans-serif; color: #550000; font-size: 12pt; font-weight:700;}
.gfont17 {font-family: 'Istok Web', sans-serif; color: #550000; font-size: 17pt;}
</style>