How does WORDPRESS modify the font size of the sidebar in STYLE? CSS？

Find the tag point that needs to be modified in your HTML file and add: style="font-size:? px； "(leave a space before the style).

Example:

& ltul id = " recentcomments " & gt

Replace with:

& ltul id = " recent comments " style = " font-size:？ px； ”& gt

It will be changed to the font size you need.