This looks like you might have an issue with the HTML code on the page. Whenever you see red coding in the page source view of FireFox, that’s an indication there was a problem the browser tried to fix. Now, each browser has it’s own method of ‘fixing’ things – some with better success than others.
Make sure you have all the appropriate closing tags: </p>, </div>, </a>, etc. If the problem only just started, think about what changes you recently made and backtrack from there. You can also try running your html through this free online utility: https://infohound.net/tidy/
After you make the changes, make sure that you clear the cache and “hard” refresh the page in your browser to be able to see the changes right away. Also, don’t forget if you have any caching WordPress plugins installed, or use a CDN (like CloudFlare) to also either clear their cache or disabled them for the time being altogether. If you’re not sure how to “hard” refresh, this site has some great tutorials on how to clear your cache: How to Clear Your Browser’s Cache Instructions.
Also check with your host and make sure that if they use a caching system above your site, that that is being cleared, too. For example: https://support.godaddy.com/help/article/8057/clearing-the-server-cache-using-website-accelerator
