Simple for loop to calculate headers size based on a specific ratio
This is what your code produces and I'm wondering if this really what you want:

"
h1 { font-size: 1.0957612059345655e+45px; }
h2 { font-size: 2.602367950332107e+22px; }
h3 { font-size: 126822144384px; }
h4 { font-size: 279968px; }
h5 { font-size: 416px; }
h6 { font-size: 16px; }"


The numbers are huge. Looking at this page, it seems you should not have base inside the multiplication here:


base *= Math.round(base*goldenRatio);



Also, by rounding at this step, you lose precision. It would be better to round right before you put the value in the string. Like this:

var base = 16;
var list = "";
for (var i = 6; i &gt; 0; i--) {
    list = "\nh" + i + " { font-size: " + Math.round(base) + "px; }" + list;
    base *= goldenRatio;
}   


I'm also wondering if you really want the \n at the start of the resulting string.
It would seem more natural to put it at the end of each line, like this:

list = "h" + i + " { font-size: " + Math.round(base) + "px; }\n" + list;


Notice also that I added more spaces around the operators in the for.
There is no real standard for this in JavaScript,
but this is a practice I borrow from other languages where it is a standard,
for improved readability. Compare these two versions, I hope you'll agree that this is an improvement:


for(var i=6; i&gt;0; i--){

for (var i = 6; i &gt; 0; i--) {