YSlow在下面显示此错误

/* Minification Failed. Returning unminified contents.
    (1442,26): run-time error CSS1019: Unexpected token,found ':'
    (1442,26): run-time error CSS1042: Expected function,26): run-time error CSS1062: Expected semicolon or closing curly-brace,found ':'
     */

这是我的捆绑代码，

bundles.Add(new StyleBundle("~/Content/css").Include(
        "~/Content/site.css","~/Content/fullcalendar.css","~/Content/jquery.dropdown.css","~/Content/jquery.tagit.css","~/Content/tipsy.css"
        ));

现在我怎么知道哪个css文件导致了这个问题？我如何调试找到导致问题的行？ site.css是我写的唯一的css文件。