If you have multiple Sitecore sites or separate environments (e.g. Development, Test, Staging), a good way to tell them apart is by setting the title on the login page.

The best way of doing this is by creating a patch file with the following contents:

<configuration xmlns:patch="http://www.sitecore.net/xmlconfig/">
  <sitecore>
    <settings>
      <setting name="WelcomeTitle">
        <patch:attribute name="value">LOGIN PAGE TITLE GOES HERE</patch:attribute>
      </setting>
    </settings>
  </sitecore>
</configuration>