Cannot Change Header Text/BG on Sidebar

I cannot seem to change the font/background of the header text in my sidebar. This is getting extremely frustrating. I’ve gone through and edided headers all throughout the CSS but nothing seem to have changed. I can’t even find h2 class=”widgettitle” in my CSS, and when I add it to my CSS it doesn’t change. It doesn’t look like there is a command code at all for altering my test/bg. Am I doing something wrong?