Anonymous 03/18/2019 (Mon) 04:59:22 No.10308 del
(32.09 KB 128x128 413446672815882250.png)
Using
document.head.innerHTML += 
<style>body{background:red;}</style>
;
is shorter and easier than GM_addStyle.
And if your problem is the font-size... Why not just increase the page's zoom? Ctrl+Scroll wheel up