document.onkeydown=nextpage

var pre=document.getElementById('pre').value;
var next=document.getElementById('pagenext').value;
var filename=document.getElementById('fname').value;
var prevpage=filename+pre+'.shtml';
var nextpage=filename+next+'.shtml';

function nextpage(event) 
{
	event = event ? event : (window.event ? window.event : null); 
	if (event.srcElement.tagName!="TEXTAREA" && event.srcElement.tagName!="INPUT" && (event.keyCode==37||event.keyCode==39)) {
	    if (event.keyCode==37) location=prevpage
	    if (event.keyCode==39) location=nextpage
	}
}