Are there any obvious errors in my stylesheet?

Hi folks. I’ve been having a few “issues” with my site, such as being unable to change hyperlink colors despite using CSS that works for others, and having strange problems with sidebars being replaced with footer widgets when making changes to the Child Theme that otherwise work fine when made to the Parent theme (I know it’s a no-no to change the Parent, which is why I want to get whatever is wrong sorted out).

I have tried installing fresh versions of Twenty Twelve, and have been through trouble-shooting steps suggested by people here and Codex. I am wondering if there might be some errors in my Stylesheet. I’ve been peering at it for days, but can’t locate anything. That doesn’t mean there are not errors staring me in the face that I’m not seeing.

I wonder if someone would mind taking a look through my CSS and seeing if anything pops out as wrong, please?

I’ve got this at the top (took name out for privacy reasons)

/*
Theme Name:     Twenty Twelve Child
Theme URI:      http://example.com/
Description:    Child theme for the Twenty Twelve theme
Author:         XXXXYYYY
Author URI:     http://perthpunk.com
Template:       twentytwelve
Version:        0.1.0
*/
@import url("../twentytwelve/style.css");

Then, the rest is as follows:

/* Images */
.alignleft {
	float: left;
}
.alignright {
	float: right;
}
.aligncenter {
	display: block;
	margin-left: auto;
	margin-right: auto;
}

.site-info {
   display: none;
}

.site-content {
    margin: 1rem 0 0;
}

body .site {
padding: 0 40px;
padding: 0 2.857142857rem;
margin-top: 0px;
margin-top: 3.428571429rem;
margin-bottom: 48px;
margin-bottom: 3.428571429rem;
box-shadow: 0 2px 6px rgba(100, 100, 100, 0.3);
}

#masthead .main-navigation ul.nav-menu,
#masthead .main-navigation div.nav-menu > ul {
	border-bottom: 0px;
	border-top: 0px;
}
#masthead .main-navigation li ul li a {
	background: lightgrey;
}
#masthead .main-navigation a {
	color: darkblue;
}
#masthead .main-navigation li ul li a:hover {
	background: #FF9933;
}
#masthead .main-navigation a:hover {
	color: #660033;
}
#masthead .main-navigation ul.nav-menu,
#masthead .main-navigation div.nav-menu > ul,
#masthead .main-navigation li ul li a {
	border-color: rgba(yellow, 0.1 );
}

@media screen and (min-width: 600px) {
 .site-content article {
  margin: 3em auto;
 }

.site-header h1 {
   font-size: 2.85714rem;
line-height: 1.84615;
font-weight: bold;
   text-align: center;
}

.site-header h2 {
   font-size: 1.3rem  ;
   text-align: center;
}

.headerimg {width:960px; margin:0 auto;}
}

@media screen and (min-width: 600px) {
.main-navigation ul.nav-menu,
    .main-navigation div.nav-menu > ul {
        display: inline-block !important;
        text-align: left;
	margin-left: 40px;
        width: 100%;
    }

.widget img {
    border-radius: 0;
    box-shadow: none;
}

.footlinks {
    text-align:center;
}

.entry-header .entry-title {
    text-align: center;
}

/* this removes the margin/space above the menu */
.main-navigation {
margin-top:0px;
}

body.page-id-85 {
 background: url("/wp-content/uploads/2013/05/HY-damned-look.gif") !important;
}

body.page-id-237 {
 background: url("/wp-content/uploads/2013/05/HY-damned-look.gif") !important;
}

body.page-id-215,body.page-id-234 {
 background: url("http://www.perthpunk.com/wp-content/uploads/2013/07/Orphans-background-550.jpg") !important;
}

body.page-id-631 {
 background: url("http://www.perthpunk.com/wp-content/uploads/2013/06/Lloyd-Memoirs-1650-3.jpg") !important;
}

body.page-id-318,body.page-id-401,body.page-id-1029,body.page-id-325,body.page-id-368,body.page-id-418,body.page-id-335,body.page-id-365,body.page-id-333,body.page-id-410,body.page-id-424,body.page-id-361 {
 background: url("http://www.perthpunk.com/wp-content/uploads/2013/06/Personal-Perspectives-backg.jpg") !important;
}

.page .site-title,
.page .site-description {
 display: none;
}

/* Assuming this is your home page */
.home .site-title,
.home .site-description {
 display: block;
}

.entry-title
 {
  display: none;
}

.page .header-image {
 display: none;
}

.home .header-image {
 display: block;
}

.wp-caption .wp-caption-text,
.gallery-caption,
.entry-caption {
	text-align: center;
}

.site-header {
padding-bottom: 0rem;
}

.header-image {
    display: block;
 margin: 2rem auto 2em;
}

.nav-menu li > a:after {
    color: #888;
    content: ' ▾';
}

.nav-menu li > a:hover:after {
    color: #444;
    content: ' ▾';
}

.nav-menu li > a:only-child:after {
    content: '';
}

.box {
   float: none;
   width: 90%;
   padding: 15px;
   margin: 10px auto;
   min-width: 200px;
   border: 3px solid black;
}

.boxlloyd {
   float: none;
   width: 90%;
   padding: 15px;
   margin: 10px auto;
   min-width: 200px;
   border: 3px solid black;
   background-color:#9f9;
}

.boxletter {
   float: none;
   width: 90%;
   padding: 15px;
   margin: 10px 10px 3.42858rem;
   min-width: 200px;
   background-color: #EEE8AA;
   border: 3px solid black;
}

@media screen and (min-width: 978px) {
.parawrapnot {
clear:both;
margin-bottom: 1.71429rem;
}

}
}

.ednotes {
    color: #0000FF;
    font-size: 0.8rem;
    line-height: 1.1rem;
    text-align: justify;
    position: relative;
    left: 16px;
    margin-top: -1.75rem;
    margin-right: 32px;
    margin-bottom: 1.71429rem;
}

.ednoteslist {
    color: #0000FF;
    font-size: 0.8rem;
    line-height: 1.1rem;
    text-align: justify;
    position: relative;
    left: 50px;
    margin-right: 100px;
    margin-bottom: 1.71429rem;
}

.edcomments {
    color: #0000FF;
    font-size: 0.9rem;
    line-height: 1.2rem;
    text-align: justify;
    position: relative;
    left: 50px;
    margin-top: -0.75rem;
    margin-right: 100px;
    margin-bottom: 1.71429rem;
}

.quotes {
  font-size: .9rem;
  line-height: 1.1rem;
  text-align: justify;
  position: relative;
  left: 16px;
  margin-right: 32px;
  margin-bottom: 1.71429rem;
}

.quotes2 {
  color: #FF0000;
  font-size: .9rem;
  line-height: 1.2rem;
  text-align: justify;
  position: relative;
  left: 40px;
  margin-right: 80px;
  margin-bottom: 1.71429rem;
}

.quotes3 {
  color: #FF0000;
  font-size: .9rem;
  line-height: 1.2rem;
  text-align: justify;
  position: relative;
  left: 40px;
  margin-right: 80px;
  margin-bottom: 3.4rem;
}

.entry-content img, .comment-content img, .widget img, img.header-image, .author-avatar img, img.wp-post-image {
    border-radius: none !important;
    box-shadow: none !important;
}

Not expecting a detailed analysis – just thought more tech-savvy folk might notice any obvious errors immediately.

Cheers
Ross