how to trim css code to just one line

how to trim css code to just one line

My client is fussy about his website loading speed. I think one way is to
trim css code to just one line. For example:
tr th{
border-bottom: 1px solid;
text-align: left;
}
tr th, tr td{
padding: 9px 20px;
border-right: 1px solid;
}
to
tr th{border-bottom: 1px solid;text-align: left;}tr th, tr td{padding: 9px
20px;border-right: 1px solid;}
How do you guys normal trim it? I use dreamweaver to write css code.
Also, I found Youtube's css link is like
"http://s.ytimg.com/yts/cssbin/www-home-c4-2x-vflt3qrMn.css", is there
benefits? Cheers.