Great question! 404 errors happen for pretty common reasons - most of which are totally preventable once you know what to look for:
Broken or dead links are the biggest culprit. Maybe you deleted a page but forgot to remove the links pointing to it. It's like having directions to house that's been torn down!
Typos in URLs happen more than you'd think. Sometimes it's a user mistyping the web address, but often it's actually a mistake in your own website links. One wrong letter and boom - 404 error.
Moving pages without setting up redirects is another classic mistake. You relocate content to a new URL but don't tell anyone where it went. Your visitors (and Google) are left standing at an empty doorstep.
Old bookmarks and external links can haunt you for years. Someone bookmarked your page in 2019, or another website linked to you, and now those links point to content that no longer exists.
Finally, website redesigns or restructuring often create a mess of 404s if you don't carefully update all your internal links to match the new layout. It's like rearranging your entire house but not updating the room numbers!
