Hello friends from Smartaddons,

I basically want to modify a couple of things in the CSS styles that load on the head section. I've been searching for hours where can I find this few lines of styles, and I'm blowing my brains out already. Where can I find this styles to be able to modify them??
I've already find out that this CSS lines are added within the php file located in: libraries/joomla/document/html/renderer/head.php, in line 154 specifically, but I'm not very good with php so I don't quite understand what's going on there.
Please, please, can somebody tell me where can I modify this small piece of CSS style!? Next I attach the CSS style:

#yt_component .items-leading .item-image{
width:300px;
max-width:100%;
min-height:60px;
}
#yt_component .items-row .item-image{
width:180px;
max-width:100%;
min-height:60px;
}

body.sj_joomla3{font-size:12px}
body.sj_joomla3{font-family:trebuchet,sans-serif;}
h1,h2,h3,h4,h5,h6{font-family:PT Sans, serif !important}

body.sj_joomla3{
background-color:#ffffff ;
color:#666666 ;
}
#yt_slideshow:after{
background-color:#ffffff ;
}
body.sj_joomla3 a{
color:#28ab00 ;
}
#yt_slideshow,
#yt_header{
background-color:#e3e3e3 ;
}
#yt_footer,
#yt_spotlight2{
background-color:#2b570c ;