I tried to edit your CSS live in FireBug and it works. Maybe you are doing it wrong. Try to edit this rule to the theme’s custom.css file.
You can do this with CSS. Add
#logo a:hover img {
opacity: 0.3;
}
If you want smoother animation, you can use CSS transitions.
Or you can try:
.commentlist > li:before {
display:none;
}
