Many of us have moved our blog at least for once from one host to another or some time have made major changes that could result into change in the structure of the permalink or some broken URLs.  If most of your traffic on your blog was from search engin then you will notice many 404 errors log in your blog statics and a gradual decrease in your website visitors as they are unable to find what they were looking for on your blog. 404 errors also consume more compution power of your server and slow down the server.  In order to fix this I would recommend the following tips.

1. Creat a 404.php file in your wp-content folder

2. copy the following basic code

<?php get_header(); ?>

<div id=”content” class=”narrowcolumn”>

<h2 class=”center”>Error 404 – Not Found</h2>

</div>

<?php get_sidebar(); ?>

<?php get_footer(); ?>

3. Now between the         <h2 class=”center”>Error 404 – Not Found</h2> you can write whatever you like to tell the web visitors

4. I would suggest adding the seach form box on 404.php so that your visitor can search you blog internally what they are looking for

5. Last but not the least I would recommend usung smart 404 plugin