Free links to your site: I admit that the title of this post is a little sensational but that is how Matt Cutts puts it. In the post linked above, he talks about the newly introduced feature of Google Webmaster Portal that allows users to find the pages that link to 404 pages on your site. In his words (emphasis his) “Some of the easiest links you’ll ever get are when people tried to link to you and just messed up.”
What was most useful for me in that post was a link to another post on the Google Webmaster Portal that helps you create better 404 pages using an experimental widget. Now I am sure there are ways to incorporate a Custom Search within the 404 without using the widget but I stuck with it because the output looked useful. Quick Online Tips had a post on the Google Custom 404 widget a couple of months ago that also talks about this widget.
This link to a fictitious “hotmail” page is an example of the output that our 404.php (in the theme folder) at weblogtoolscollection.com generates. We still need to fix the footer and the sidebars but it works for now.