By "Search Box", what do you mean? I have provided you with a number of solutions. Follow the instructions I provided and you should be on your way.
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Google Search Box
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Here is some HTML code for Google Search Box, past it into your site. It will search google and display results after a user searches for something, from your site.
<FORM method=GET action="http://www.google.co.uk/search">
<input type=hidden name=ie value=UTF-8>
<input type=hidden name=oe value=UTF-8>
<A HREF="http://www.google.co.uk/">
<IMG SRC="http://www.google.co.uk/logos/Logo_40wht.gif"
border="0" ALT="Google" align="absmiddle"></A>
<INPUT TYPE=text name=q size=25 maxlength=255 value="">
<INPUT type=submit name=btnG VALUE="Google Search">
</FORM>
(Slightly cut down by me)
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Your own search engine
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If you would like to run your own search engine, please download my own script and get going with your own PHP and MYSQL search engine (Will run on Dhost). To download the script, please click
here.
How to installEdit the first few lines of the script to be right for your site. On the Dhost control panel, click phpmyadmin. Select your search database and run the "SQL" script which comes with your search engine.
FeaturesYour search engine will search the MYSQL database and entries can be added by people submitting their site on the homepage.
ErrorsIf you have any problems, please email me
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Search Your Site
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If you wish for users to be able to search your site, try
Freefind. Browse their site and signup to the site search. Paste the HTML they provide onto your site and enjoy.
I hope this post helps you. If you have any questions, please email me.
Thanks,
Icey

*Pheww that was huge - boost my rep if you found that post helpful*