Add CSS doesn't change anything

Website url?

It’s https://jeremysarber.com

Thanks.

It seems that everything is ok, but some css rules are “stronger”.

try this, to check:

#upprev_box
{
    border-left: 20px solid #651111 !important;
}

No change. But I’m also finding that I am unable to change the styles of other plugins as well. I’m perplexed.