How can I remove the author box for the narrow width

#author-box and #author-info are not CSS selectors we use. You should use .ts-fab-wrapper instead.

Thanks.
I tried, but it does not work.
I changed as follows:
.ts-fab-wrapper { display: none; }

I’m using Fancier Author box.

Can you post your website URL?

sure, for example, https://www.leunkim.com/routine/hyehwa

Where have you added this code? I don’t see it loading.

I added the code on my CSS as

@media (max-width: 776px) {
#page{clear:both; max-width:600px; !important; padding:0; !important; margin:auto; overflow:hidden; margin-top:15px; margin-bottom:15px;}

#primary{max-width:600px; padding:0; margin:0 0 0 20px;}
#banners2 {display:none;}
#secondary {display: none;}
#ts-fab-wrapper {display:none;}
.ts-fab-wrapper {display:none;}
#ts-fab {display:none;}
.ts-fab {display:none;}
#main #content {max-width: 560px; margin:auto; padding: 0;}
.commentlist {width: 100%;}
.commentlist > li.comment,
.commentlist .pingback {margin-left: 50px;width: auto;}
}

hi I have resolved this topic.
Sorry, my site was using cache also for CSS files.
Thank you very much.