The front end font cannot be changed

[ShuaiShao20010902]

I find that in css，some fonts do not change in the web page after using the change of font-size, colour. I can't figure it out. What's the reason

[ShuaiShao20010902]

Okey, I I figure it out. In my html file, I need to redefine a selection for a single area, like this <section class="cat-introduction">，If I don't, it will be affected by the overall css, so I can't change other properties.