Twenty Twelve Reverted my changes

Hi, I’m experiencing an extremely frustrating situation with my Twenty Twelve Child theme. I was attempting to add some new code to it today and it suddenly reverted all the changes I’d previously made, most of which were done with the help of kind people on this forum. So the grey lines came back, the hyperlink in the bottom right-hand corner reverted back to blue and generally ruined everything I’ve done to my site.

I have no idea why all my changes have been undone. I barely touched the code, just tried to insert some new lines at the top. Can someone see something obvious out of place in this bit of code that force Twenty Twelve to disregard all the previous changes I’ve made to my child?

§/*
Theme Name: Twenty Twelve Child
Theme URI: http://example.com/
Description: Child theme for the Twenty Twelve theme
Author: Your name here
Author URI: http://example.com/about/
Template: twentytwelve
Version: 0.1.0
*/

@import url(“../twentytwelve/style.css”);
.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;
.main-navigation {
display: none;
}
body {
line-height: 0;
}
div.entry-content table tbody tr td h3 span a
{
color: #FB4105
}
.entry-content table, .comment-content table
{
border: none;
}
.entry-content td
{
border: none;
}
.site-content article {
border-bottom: 0;
margin-bottom: 0;
padding-bottom: 0;
}
#colophon {
border: 0;
}§