thank you for your response, i check through my issue again, find out the issue really is:
i have six navigation buttons, only for one button when i click it, then change all the content of the webpage including all buttons into a different font and all the posts in that category. if I click any of the other navigation buttons, then font of the buttons and the content of the page will bring back to the original button font.
i hope this detail will help you have a better understanding. thank you!
best
jay