JavaScript - Desperate Help Enabling Disabled Button In Slideshow

	var displayWaitMessage=true;	// Display a please wait message while images are loading?


	var activeImage = false;
	var imageGalleryLeftPos = false;
	var imageGalleryWidth = false;
	var imageGalleryObj = false;
	var maxGalleryXPos = false;
	var slideSpeed = 0;
	var imageGalleryCaptions = new Array();
	function startSlide(e)
	{
		if(document.all)e = event;
		var id = this.id;
		if(this.id=='arrow_right'){
			slideSpeedMultiply = Math.floor((e.clientX - this.offsetLeft) / 5);
			slideSpeed = -1*slideSpeedMultiply;
			slideSpeed = Math.max(-10,slideSpeed);
		}else{
			slideSpeedMultiply = 10 - Math.floor((e.clientX - this.offsetLeft) / 5);
			slideSpeed = 1*slideSpeedMultiply;
			slideSpeed = Math.min(10,slideSpeed);
			if(slideSpeed<0)slideSpeed=10;
		}
	}

	function releaseSlide()
	{
		var id = this.id;
		slideSpeed=0;
	}

	function gallerySlide()
	{
		if(slideSpeed!=0){
			var leftPos = imageGalleryObj.offsetLeft;
			leftPos = leftPos/1 + slideSpeed;
			if(leftPos>maxGalleryXPos){
				leftPos = maxGalleryXPos;
				slideSpeed = 0;

			}
			if(leftPos<minGalleryXPos){
				leftPos = minGalleryXPos;
				slideSpeed=0;
			}

			imageGalleryObj.style.left = leftPos + 'px';
		}
		setTimeout('gallerySlide()',20);

	}

	function showImage()
	{
		if(activeImage){
			activeImage.style.filter = 'alpha(opacity=50)';
			activeImage.style.opacity = 0.5;
		}
		this.style.filter = 'alpha(opacity=100)';
		this.style.opacity = 1;
		activeImage = this;
	}

	function initSlideShow()
	{
		document.getElementById('arrow_left').onmousemove = startSlide;
		document.getElementById('arrow_left').onmouseout = releaseSlide;
		document.getElementById('arrow_right').onmousemove = startSlide;
		document.getElementById('arrow_right').onmouseout = releaseSlide;




		imageGalleryObj = document.getElementById('theImages');
		imageGalleryLeftPos = imageGalleryObj.offsetLeft;
		var galleryContainer = document.getElementById('galleryContainer');
		imageGalleryWidth = galleryContainer.offsetWidth - 20;
		maxGalleryXPos = imageGalleryObj.offsetLeft;
		minGalleryXPos = imageGalleryWidth - document.getElementById('slideEnd').offsetLeft;

		if (navigator.userAgent.indexOf('MSIE') >= 0) {
			var arrowWidth = document.getElementById('arrow_left').offsetWidth;
			var el = document.createElement('div');
			el.style.position = 'absolute';
			el.style.left = arrowWidth + 'px';
			el.style.width = (galleryContainer.offsetWidth - arrowWidth * 2) + 'px';
			el.style.overflow = 'hidden';
			el.style.height = '100%';

			document.getElementById('galleryContainer').appendChild(el);
			el.appendChild(document.getElementById('theImages'));
		}
		var slideshowImages = imageGalleryObj.getElementsByTagName('IMG');
		for(var no=0;no<slideshowImages.length;no++){
			slideshowImages[no].onmouseover = showImage;
		}

		var divs = imageGalleryObj.getElementsByTagName('DIV');
		for(var no=0;no<divs.length;no++){
			if(divs[no].className=='imageCaption')imageGalleryCaptions[imageGalleryCaptions.length] = divs[no].innerHTML;
		}
		gallerySlide();
	}

	function showPreview(imagePath,imageIndex){
		var subImages = document.getElementById('previewPane').getElementsByTagName('IMG');
		if(subImages.length==0){
			var img = document.createElement('IMG');
			document.getElementById('previewPane').appendChild(img);
		}else img = subImages[0];

		if(displayWaitMessage){
			document.getElementById('waitMessage').style.display='inline';
		}
		document.getElementById('largeImageCaption').style.display='none';
		img.onload = function() { hideWaitMessageAndShowCaption(imageIndex-1); };
		img.src = imagePath;

	}
	function hideWaitMessageAndShowCaption(imageIndex)
	{
		document.getElementById('waitMessage').style.display='none';
		document.getElementById('largeImageCaption').innerHTML = imageGalleryCaptions[imageIndex];
		document.getElementById('largeImageCaption').style.display='block';

	}
	window.onload = initSlideShow;

<script type="text/javascript">
window.onload=function() {
  df=document.forms[0];
  df[1].disabled=true;
  df[0].onclick=function(){
  df[1].disabled=(df[1].disabled)?false:true;
  }
  df=document.forms[0];
  df[4].disabled=true;
  df[1].onclick=function(){
  df[4].disabled=(df[4].disabled)?false:true;
  }
    df=document.forms[0];
  df[5].disabled=true;
  df[4].onclick=function(){
  df[5].disabled=(df[5].disabled)?false:true;
  }
  df=document.forms[0];
  df[6].disabled=true;
  df[5].onclick=function(){
  df[6].disabled=(df[6].disabled)?false:true;
  }
  df=document.forms[0];
  df[9].disabled=true;
  df[6].onclick=function(){
  df[9].disabled=(df[9].disabled)?false:true;
  }
  df=document.forms[0];
  df[10].disabled=true;
  df[9].onclick=function(){
  df[10].disabled=(df[10].disabled)?false:true;
  }
  df=document.forms[0];
  df[12].disabled=true;
  df[10].onclick=function(){
  df[12].disabled=(df[12].disabled)?false:true;
  }
  df=document.forms[0];
  df[15].disabled=true;
  df[12].onclick=function(){
  df[15].disabled=(df[15].disabled)?false:true;
  }
  df=document.forms[0];
  df[18].disabled=true;
  df[17].onclick=function(){
  df[18].disabled=(df[18].disabled)?false:true;
  }
df = document.forms[0];  
df[2].onclick = function() {     
df[17].disabled = !df[17].disabled;     
df[18].disabled = !df[18].disabled;     
df[19].disabled = !df[19].disabled;
df[20].disabled = !df[20].disabled; } 

df[17].disabled = true; 
df[18].disabled = true; 
df[19].disabled = true;
df[20].disabled = true; 
 }
df = document.forms[0];  
df[3].onclick = function() {     
df[17].disabled = !df[17].disabled;     
df[18].disabled = !df[18].disabled;     
df[19].disabled = !df[19].disabled;
df[20].disabled = !df[20].disabled; } 

df[17].disabled = true; 
df[18].disabled = true; 
df[19].disabled = true;
df[20].disabled = true; 
</script>

<html>
<head>
<script type="text/JavaScript">
<!--
	var sam = 9;
	var sally = 8;
	var donald = 4;

function percentage (score) {
  return score / 10 * 100;
};
function go() {
  document.write("Sam's score on the test is " + percentage(sam) + "%, <br \> Sally's score on the test is " + percentage(sally) +
              "%, <br \> Donald's score on the test is " + percentage(donald) + "%");
};
function highscore() {
if (Math.max(90, 80, 40) === 90){
        document.write("Sam's score was the highest.")};
    else if (Math.max(90, 80, 40) === 80){
        document.write("Sally's score was the highest.")};
	else{
		document.write("Donald's score was the highest.")}
};
//-->
</script>
</head>
<body>
<input type="button" onclick="go()" value="Student Grades">
<br \>
<input type="button" onclick="highscore()" value="Highest Score">
</body>
</html>

if (output=="Available")
        document.register.submitBtn.disabled=false;
    else
        document.register.submitBtn.disabled=true;

<script type="text/javascript">
                                            window.onload = function(){
                                       var check = document.getElementById('check1');
                                       var file = document.getElementById('file');
                                       var text = document.getElementById('text');
                                       check . onchange = function(){
                                          if( check.checked ){
                                              text.setAttribute('disabled', 'disabled');
                                              file.removeAttribute('disabled');
                                          }
                                          else{
                                              text.removeAttribute('disabled');
                                              file.setAttribute('disabled', 'disabled');
                                          }

                                       };
                                    };
                                    
                                        </script>
                                    <input id="check1" type="checkbox" name="check" /> From link!!!<br/>
                                    Poster:<input  id="file" type="file" name="poster"  />
                                    
                                    Poster from link:<input  id="text" type="text" name="postlink" /><br/>