You have to do it by changing the percents of the gradient to smaller or larger values, #fff
= white so the range should be larger. #9CC
is the blue color, its range should be smaller.
body {
background-image: -webkit-gradient(linear, right bottom, left top, color-stop(0, #fff), color-stop(0.35, #fff), color-stop(0.35, #9CC), color-stop(0.5, #9CC), color-stop(0.5, #fff), color-stop(0.85, #fff), color-stop(0.85, #9CC));
background-image: -webkit-linear-gradient(right bottom, #fff 0%, #fff 35%, #9CC 35%, #9CCb 50%, #fff 50%, #fff 85%, #9CC 85%);
background-image: -moz-linear-gradient(right bottom, #fff 0%, #fff 35%, #9CC 35%, #9CC 50%, #fff 50%, #fff 85%, #9cc 85%);
background-image: -ms-linear-gradient(right bottom, #fff 0%, #fff 35%, #bbb 35%, #bbb 50%, #fff 50%, #fff 85%, #bbb 85%);
background-image: -o-linear-gradient(right bottom, #fff 0%, #fff 35%, #9CC 35%, #9CC 50%, #fff 50%, #fff 85%, #9CC 85%);
filter: progid:DXImageTransform.Microsoft.gradient(startColorstr='#ffffff', endColorstr='#9CC', GradientType=0);
/ IE6-8 */ background-image: linear-gradient(right bottom, #fff 0%, #fff 35%, #9CC 35%, #9CC 50%, #fff 50%, #fff 85%, #9CC 85%);
background-size: 5px 5px;
width:100%;
height:100%;
}
I changed the 25%
to 35%
and 75%
to 80%
correspondingly which lessened the range and therefore width of the blue lines and increased the range and therefore the width of the white lines
To change them yourself you may want to use a find and replace tool