Inference rules in HTML

I hacked together a javascript function to make it easy to write inference rules in HTML. For example, to generate this:

a→b     b→c
	HYP-SYL
a→c

I just have to write this:

rule("HYP-SYL", ["a→b", "b→c"], "a→c"])

Here's the function:

function rule(name, top, bottom) {
    var top = top.join("     ");
    document.write(
        "<p><table cellpadding=0>" +
        "<tr>" +
            "<td align=center>\n" + top + "</td>" +
            "<td></td>" +
        "</tr>" +
        "<tr style='line-height:0.1'>" +
            "<td align=center'>" +
                "<div style='border-bottom: solid 1px #000'></div>" +
            "</td>" +
            "<td> " +
                // position:relative is necessary to prevent IE from
                // clipping off the top and bottom of the name
                "<span style='position:relative'><tt>"+name+"</tt></span>"+
                "</td>" +
        "</tr>\n" +
        "<tr>" +
            "<td align=center>\n" + bottom + "</td>" +
            "<td></td>" +
        "</tr>" +
        "</table></p>"
    )
}

I hope someone out there finds it useful.