Whenever you make a web page, check that it is free of errors...

Once you make a web page, don't assume it is ready to go live and be published on your website, ready for all site visitors to see/read.
Ask a friend to test your web page in a location on your website thats not known to anyone else except you and your friend. Your friend might find errors using a different web browser - this is all valuable feedback.
If you do find an error, make a web page that is the same but change a few things at a time and get your trusted friend to test the page again.
You'd be surprised how many people make a web page, then assume it is free of errors because it looks fine in their web browser - this is a mistake.
Don't make the same mistake the next time you make a web page.