It's what happens when an address refers to something that's not there (it can't find what you asked for, where your request said it should have been).
There's various reasons why, here's a couple:
It isn't there. What the address referred to has been removed. Perhaps permanently, or perhaps it's been relocated and nobody's done anything to update what linked to it, nor configured the server to redirect visitors to its new location.
The address was incorrect. This is usually due to a typing error on someone else's pages leading to the site (spelling errors; incorrect use of lower or upper case letters; adding, or removing, leading or trailing slashes, etc.).
NB: The policy for addresses on this website is to use all lower-case letters, use the hyphen between words (where there'd, normally, be blank spaces), and generally avoid anything that requires using the shift key. Anybody writing links to this website should read the info page about linking to here.
If it's a broken link on a page within www.cameratim.com website, it needs fixing, and you can send the webmaster a message to bring it to their attention.
If you arrived here from a link on another website, it's that other website that needs fixing (you'd have to find a way to contact them about it).
NB: Search engines should eventually fix up their links by themselves.
If you were hand-typing an address in, you might want to:
Check whether you've got it right.
Try slightly modifying what you typed in—add or remove a slash, spell things correctly, use all lower-case letters, etc.
If you're looking at things mentioned in web page source code, pay attention to addresses starting with a slash. They start from the domain name, not from within a sub-directory.
Look through the menus on this website to find it.
You could try using a search engine to search through the contents of this website.