function checkframes() {
	// define constants
	var site_url = "http://sine.ncl.ac.uk:9999/"
	var site_url2 = "http://cpol.ncl.ac.uk/"
	var site_url3 = "http://www.churchplansonline.org/"
	var site_url4 = "http://www.churchplansonline.org.uk/"
	var site_url5 = "http://www.churchplansonline.com/"
	var site_url6 = "http://www.churchplansonline.net/"
	var site_url7 = "http://www.icbs.org.uk/"
	var index_url = site_url + "index.htm"
	var index_url2 = site_url2 + "index.htm"
	var index_url3 = site_url3 + "index.htm"
	var index_url4 = site_url4 + "index.htm"
	var index_url5 = site_url5 + "index.htm"
	var index_url6 = site_url6 + "index.htm"
	var index_url7 = site_url7 + "index.htm"
	var indexasp_url = site_url + "index.asp"
	var indexasp_url2 = site_url2 + "index.asp"
	var indexasp_url3 = site_url3 + "index.asp"
	var indexasp_url4 = site_url4 + "index.asp"
	var indexasp_url5 = site_url5 + "index.asp"
	var indexasp_url6 = site_url6 + "index.asp"
	var indexasp_url7 = site_url7 + "index.asp"

	// define variables
	var button_needed_flg = true
	var top_url = top.document.location.href
	var siteurlstr_len = indexasp_url.length
	if (document.images) { // check if images can be accessed

		// check if top url is correct frames
		if ((top_url == site_url) | (top_url == site_url2) | (top_url == site_url3) | (top_url == site_url4) | (top_url == site_url5) | (top_url == site_url6) | (top_url == site_url7) | (top_url == index_url) | (top_url == index_url2) | (top_url == index_url3) | (top_url == index_url4) | (top_url == index_url5) | (top_url == index_url6) | (top_url == index_url7) | (top_url == indexasp_url) | (top_url == indexasp_url2) | (top_url == indexasp_url3) | (top_url == indexasp_url4) | (top_url == indexasp_url5) | (top_url == indexasp_url6) | (top_url == indexasp_url7)) {
			button_needed_flg = false
		} else {
			if (top_url.length >= siteurlstr_len) {
				if (top_url.substring(0,siteurlstr_len) == indexasp_url) {
							button_needed_flg = false
				}
			}
		}

		if (!button_needed_flg) {
			// if correct, hide button which loads correct url
			// to reload this page in the new frames...
			document.images["hideme"].src="/images/misc/nought.gif"
			document.images["hideme"].width = 0
			document.all["navbar"].className="navbarhidden"
		}
	}
}