Scroll-up

/****** Librería Jquery ******/
.....::::Incluirla para que funcione el chiste::::.....

/****** Javascript ******/

/**
 * jQuery.ScrollTo - Easy element scrolling using jQuery.
 * Copyright (c) 2007-2009 Ariel Flesler - aflesler(at)gmail(dot)com | http://flesler.blogspot.com
 * Dual licensed under MIT and GPL.
 * Date: 5/25/2009
 * @author Ariel Flesler
 * @version 1.4.2
 *
 * http://flesler.blogspot.com/2007/10/jqueryscrollto.html
 */
;(function(d){var k=d.scrollTo=function(a,i,e){d(window).scrollTo(a,i,e)};k.defaults={axis:'xy',duration:parseFloat(d.fn.jquery)>=1.3?0:1};k.window=function(a){return d(window)._scrollable()};d.fn._scrollable=function(){return this.map(function(){var a=this,i=!a.nodeName||d.inArray(a.nodeName.toLowerCase(),['iframe','#document','html','body'])!=-1;if(!i)return a;var e=(a.contentWindow||a).document||a.ownerDocument||a;return d.browser.safari||e.compatMode=='BackCompat'?e.body:e.documentElement})};d.fn.scrollTo=function(n,j,b){if(typeof j=='object'){b=j;j=0}if(typeof b=='function')b={onAfter:b};if(n=='max')n=9e9;b=d.extend({},k.defaults,b);j=j||b.speed||b.duration;b.queue=b.queue&&b.axis.length>1;if(b.queue)j/=2;b.offset=p(b.offset);b.over=p(b.over);return this._scrollable().each(function(){var q=this,r=d(q),f=n,s,g={},u=r.is('html,body');switch(typeof f){case'number':case'string':if(/^([+-]=)?\d+(\.\d+)?(px|%)?$/.test(f)){f=p(f);break}f=d(f,this);case'object':if(f.is||f.style)s=(f=d(f)).offset()}d.each(b.axis.split(''),function(a,i){var e=i=='x'?'Left':'Top',h=e.toLowerCase(),c='scroll'+e,l=q[c],m=k.max(q,i);if(s){g[c]=s[h]+(u?0:l-r.offset()[h]);if(b.margin){g[c]-=parseInt(f.css('margin'+e))||0;g[c]-=parseInt(f.css('border'+e+'Width'))||0}g[c]+=b.offset[h]||0;if(b.over[h])g[c]+=f[i=='x'?'width':'height']()*b.over[h]}else{var o=f[h];g[c]=o.slice&&o.slice(-1)=='%'?parseFloat(o)/100*m:o}if(/^\d+$/.test(g[c]))g[c]=g[c]<=0?0:Math.min(g[c],m);if(!a&&b.queue){if(l!=g[c])t(b.onAfterFirst);delete g[c]}});t(b.onAfter);function t(a){r.animate(g,j,b.easing,a&&function(){a.call(this,n,b)})}}).end()};k.max=function(a,i){var e=i=='x'?'Width':'Height',h='scroll'+e;if(!d(a).is('html,body'))return a[h]-d(a)[e.toLowerCase()]();var c='client'+e,l=a.ownerDocument.documentElement,m=a.ownerDocument.body;return Math.max(l[h],m[h])-Math.min(l[c],m[c])};function p(a){return typeof a=='object'?a:{top:a,left:a}}})(jQuery);

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/****** Javascript ******/

$(window).scroll(function(){
		if (window.pageYOffset >= 700) {//Regular desde donde aparecerá la flecha
			$('#scroll-up:not(:visible)').fadeIn();
		} else {
			$('#scroll-up:visible').fadeOut();
		}
});

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/****** Estilos CSS ******/

/* SCROLL-UP */
#scroll-up {
	display: none;
	width: 40px;
	height: 40px;
	position: fixed;
	top: 10px;
	right: 10px;
	opacity: 0.5;
	background: transparent url("../imgs/irArribaFlecha.png") top left no-repeat;
}

#scroll-up:hover {
	opacity: 0.7;
}

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/****** HTML (Esto abajo del todo de la página) ******/

<div class="floatRight">
	<a onclick="$('body').scrollTo(0)" class="irArriba"><strong>Ir arriba</strong></a>
</div>