Timeliness

If you can't find when the information was written, it should make you question its reliability

You will need to determine whether or not timeliness is important for your topic.

Sometimes whether or not information is current is not important--we still read Shakespeare, for example--but for most topics, you need to decide if more recent information means that an older source is now inaccurate.

The most obvious examples are in science and technology. An article on computers from 1989 may be interesting from a historical perspective, but you wouldn't want to buy a new PC based on it.

Recent information is also very important in business, in government decision-making, and in gathering statistics for social issues.

It's rare for a paper source not to include a publication date. Unfortunately it is very common for a web page to not have any information about when it was posted or updated. If you can't find this information, it should make you question its reliability.

Primary sources were written at the time of the event by people directly involved.

In history, the role of primary sources is very large. These are sources that were written at the time of an event, often by people directly involved. There are a lot of primary sources on the web. The journal of a soldier in the Civil War is an example (below).