Codigo Html 

<!-- Copiar dentro del tag BODY -->
<form action="http://blogsearch.google.com/blogsearch" method="get">
<input type=hidden name="bl_url" value="<$BlogURL$>">
<label for="search" accesskey="4">Search this blog:</label>
<br/>
<input id="search" name="as_q" size="15" type="text" size="20"/>
<br/>
<input value="Search" name="submit" type="submit"/>
</form>