What does a "404 error" mean?

When you come across a 404 error one of three things has probably happened:

• You have typed the address in incorrectly. Compare the address showing in the bar at the top of your screen to whatever your source was. If there are mistakes, fix them and try again.
• You have followed an old link to information that has moved. This is unfortunately all too common on the web because sites reorganise and disappear frequently.
• You have tried to access a page that your ISP (internet service provider) has blocked for including potentially illegal material on the recommendation of the Internet Watch Foundation.

In either of the first two cases, the first thing to do is usually to look around the site to find related information. The page you're looking for could have been updated or superseded, and in most cases the information you actually want will be in the newer version.

But if you have no luck, or if what you need is the older version, then:

• If the link you followed was from another site but not a search engine, go back to the previous site and copy the description of the link you followed into a search engine. If the page is available at a different location, the search engine should be able to find it.
• If the link you followed was from a search engine, like Google, that stores web pages in a cache, try clicking on the link that says ’Cache’ instead of the link to the actual page. Sometimes the information you want will be stored there.
• If not, try the Internet Archive's Wayback Machine. Copy the address you were looking for (not the 404 address!) into the box. You will be able to retrieve a listing of the pages that were at that address on the various dates in the past when the Internet Archive stored them. Not everything is retrievable in this way - the Archive does delete material if requested.

If you still can't find the page it's time to formulate a search that will get you something else which is just as good.