Removing unauthorised scripts from your site can be tricky. If you want to have a go at finding it read on!

<p>(from <a href="http://www.webdevelopersnotes.com/tips/html/automatically_redirecting_visitors_to_another_page_.php3">http://www.webdevelopersnotes.com/tips/html/automatically_redirecting_visitors_to_another_page_.php3</a>)</p>
<p>It might so happen that during the <a id="KonaLink0" class="kLink" href="http://www.webdevelopersnotes.com/tips/html/automatically_redirecting_visitors_to_another_page_.php3">web site</a> maintenance process, you might rename a page or move it to another location. One of your kind visitors (rare!) informs you that he/she stumbled on this page and it shows a "404 page not existing error".<br /> Think about other users who have 'bookmarked' this page or worse still, <a id="KonaLink1" class="kLink" href="http://www.webdevelopersnotes.com/tips/html/automatically_redirecting_visitors_to_another_page_.php3">search engines</a> that have indexed this page.

After my own site was attacked this is great advice from 25yearsofprogramming.com (now offline). This article discusses how to prevent your site from getting hacked, how to repair a damaged site plus website security precautions.