As You can see I've added Google search for indexing this website. The pice of html code written into the sidebar page is simple.

<!-- Google Search -->
<form method="get" action="" style="text-align: center;">
<img src="img/google.png" /><br />
<input type="text" name="q" size="20" maxlength="255" value="" />
<input type="hidden" name="sitesearch" value="" />
<input type="submit" value="Search" />
<!-- End Google Search -->

The input field "sitesearch" filters the search only on my website, as It happens when you search google with the extension "site:searchonlythissite.zzz" in the search text.

Another piece of simple html code for searching with Yahoo:

<!-- Yahoo! Search -->
<form method=get action="">
<table cellpadding=0 cellspacing=0 border=0>
<tr><td><div style="border: 1px solid #999; padding: 5px;"><center><a href="">
<img src="" border=0></a><br>
<input type="text" name="p" size=19 style="margin: 10px 0 0 0"><br><font size="-2" face="arial, helvetica">
<input type="radio" name="vs" style="vertical-align: middle" value="">Search the web<br>
<input type="radio" name="vs" style="vertical-align: middle" value="" checked>Search this site</font><br>
<input type="hidden" name="fr" value="yscpb">
<input type="submit" value="Search" style="margin: 5px 0 0 0"></center></div></td></tr>
<!-- End Yahoo! Search -->

It's obvious you have to change into your domain.