[JavaScript] テーブルのセルとかに斜めの線（打ち消し線？）をひくjQueryプラグインです。CSSのtransformが使えるブラウザのみ。

jquery.diagonaline.js

/*

$('table thead th').diagonaline({
    color:'#666',//線の色
    leftTop:true//線を左上から右下にひく場合はtrue、逆はfalse
});
*/

(function($){
	// CSS3 Transformに対応しているかどうか
	var ds = document.createElement("div").style,
	notSupport=(
		!('transform' in ds)
		&& !('webkitTransform' in ds)
		&& !('mozTransform' in ds)
		&& !('oTransform' in ds)
		&& !('msTransform' in ds)
	);
	
	$.fn.diagonaline = function (conf) {
		if(notSupport){
			return false;
		}
		
		var c = $.extend({
			color:'#666',
			leftTop:true
		},conf),
		color = c.color,
		base = (c.leftTop ? '' : '-');
		
		return this.each(function(){
			var cell = $(this);
			if(cell.is(':empty')){
				cell.html(' ');
			}
			
			var pt = Number(cell.css('paddingTop').replace('px','')),
			pl = Number(cell.css('paddingLeft').replace('px','')),
			cw = cell.outerWidth(),
			ch = cell.outerHeight(),
			nh = Math.sqrt(cw*cw + ch*ch),
			nr = Math.atan2(ch,cw),
			ns = (nr*360/(2*Math.PI)),
			nhm = (nh/2),
			op = Math.sin(nr)*nhm,
			ad = Math.sqrt((nhm*nhm) - (op*op)),

			html = '<s style="';
			html += 'height:1px;';
			html += 'display:block;';
			html += 'position:absolute;';
			html += 'background:'+color+';';
			html += 'width:'+nh+'px;';
			html += '-webkit-transform:rotate('+base+ns+'deg);';
			html += '-moz-transform:rotate('+base+ns+'deg);';
			html += '-ms-transform:rotate('+base+ns+'deg);';
			html += '-o-transform:rotate('+base+ns+'deg);';
			html += 'transform:rotate('+base+ns+'deg);';
			html += '-sand-transform:rotate('+base+ns+'deg);';
			html += 'margin-top:-'+(pt==0 ? Math.floor(op/2) : op-pt)+'px;';
			html += 'margin-left:-'+(pt==0 ? Math.floor((nhm-ad)/2) : nhm-ad+pl)+'px;';
			html += '"></s>';
			
			cell.append(html);
		});
	};
})(window.jQuery);

jquery.diagonaline.min.js

(function(c){var b=document.createElement("div").style,a=(!("transform" in b)&&!("webkitTransform" in b)&&!("mozTransform" in b)&&!("oTransform" in b)&&!("msTransform" in b));c.fn.diagonaline=function(e){if(a){return false}var g=c.extend({color:"#666",leftTop:true},e),d=g.color,f=(g.leftTop?"":"-");return this.each(function(){var p=c(this);if(p.is(":empty")){p.html("&nbsp;")}var s=Number(p.css("paddingTop").replace("px","")),j=Number(p.css("paddingLeft").replace("px","")),k=p.outerWidth(),h=p.outerHeight(),i=Math.sqrt(k*k+h*h),o=Math.atan2(h,k),n=(o*360/(2*Math.PI)),r=(i/2),m=Math.sin(o)*r,q=Math.sqrt((r*r)-(m*m)),l='<s style="';l+="height:1px;";l+="display:block;";l+="position:absolute;";l+="background:"+d+";";l+="width:"+i+"px;";l+="-webkit-transform:rotate("+f+n+"deg);";l+="-moz-transform:rotate("+f+n+"deg);";l+="-ms-transform:rotate("+f+n+"deg);";l+="-o-transform:rotate("+f+n+"deg);";l+="transform:rotate("+f+n+"deg);";l+="-sand-transform:rotate("+f+n+"deg);";l+="margin-top:-"+(s==0?Math.floor(m/2):m-s)+"px;";l+="margin-left:-"+(s==0?Math.floor((r-q)/2):r-q+j)+"px;";l+='"></s>';p.append(l)})}})(window.jQuery);