Yahoo CSS Reset + Yahoo Base (i've changed a little the default padding/margin with headings) + Minimal helpers: Clearfix (.cfix), Float (.fl, .fr, .clear), Horizontal Lists (ul.hl, ol.hl), List separator (li.sep, li.separator) helpers.

css_base.css

html{color:#000;background:#FFF}body,div,dl,dt,dd,ul,ol,li,h1,h2,h3,h4,h5,h6,pre,code,form,fieldset,legend,input,button,textarea,select,p,blockquote,th,td{margin:0;padding:0}table{border-collapse:collapse;border-spacing:0}fieldset,img{border:0}address,button,caption,cite,code,dfn,em,input,optgroup,option,select,strong,textarea,th,var{font:inherit}del,ins{text-decoration:none}li{list-style:none}caption,th{text-align:left}h1,h2,h3,h4,h5,h6{font-size:100%;font-weight:normal}q:before,q:after{content:''}abbr,acronym{border:0;font-variant:normal}sup{vertical-align:baseline}sub{vertical-align:baseline}legend{color:#000}body{font:13px/1.231 arial,helvetica,clean,sans-serif;*font-size:small;*font:x-small}select,input,textarea,button{font:99% arial,helvetica,clean,sans-serif}table{font-size:inherit;font:100%}pre,code,kbd,samp,tt{font-family:monospace;*font-size:108%;line-height:100%}h1{font-size:138.5%}h2{font-size:123.1%}h3{font-size:108%}h1,h2,h3{padding:0 0 0.5em}h1,h2,h3,h4,h5,h6,strong,dt{font-weight:bold}optgroup{font-weight:normal}abbr,acronym{border-bottom:1px dotted #000;cursor:help}em{font-style:italic}del{text-decoration:line-through}blockquote,ul,ol,dl{margin:1em}ol,ul,dl{margin-left:2em}ol{list-style:decimal outside}ul{list-style:disc outside}dl dd{margin-left:1em}th,td{border:1px solid #000;padding:.5em}th{font-weight:bold;text-align:center}caption{margin-bottom:.5em;text-align:center}sup{vertical-align:super}sub{vertical-align:sub}p,fieldset,table,pre{margin-bottom:1em}button,input[type="checkbox"],input[type="radio"],input[type="reset"],input[type="submit"]{padding:1px}img{-ms-interpolation-mode:bicubic}pre {overflow: hidden;}
/* Helpers */
ul.hl,ol.hl{list-style-type:none;padding:0;margin:0}ul.hl li,ol.hl li{float:left;text-align:center;margin:0 0 0 0.5em;}ul.hl li.fr, ol.hl li.fr{float: right;}.cfix:after{content:".";display:block;height:0;clear:both;visibility:hidden}.cfix{display:inline-block}* html .cfix{height:1%}.cfix{display:block}ul.hl:after,ol.hl:after{content:".";display:block;height:0;clear:both;visibility:hidden}ul.hl,ol.hl{display:inline-block}* html ul.hl,* html ul.hl ol.hl{height:1%}ul.hl,ol.hl{display:block}.fl {display: block;float: left;} .fr{display: block;float: right}li.separator,li.sep{display:block;height:1em;visibility:hidden}.clear{clear:both}
ul.hl li:first-child,ol.hl li:first-child{margin:0;}