Re-position Recent Posts Widget

I would like to raise the Recent Posts Widget on the page so that there is less white space above it. Site is in Hebrew, recent posts widget is in right hand sidebar, below Youtube video:

http://www.photomobil.co.il

I have tried all of the following snippets in my custom.css file and none of them worked:

.custom li.widget {margin-bottom:-20px !important;}

.widget-area .widget {
  margin-bottom: 3.8rem;
}

#recent-posts-5.widget_recent_entries
{
position:relative;
top: -40px;
font-family: Arial
}

Thanks in advance for any help.