var a1 = "aa";
var a2 = "a";
var b1 = "americanab";
var b2 = "stractarti";
var b3 = "sts.org";
var sign = "@";
var addr = a1 + a2 + sign + b1 + b2 + b3;
document.write('<a href="' + 'mai' + 'lto:' + addr + '?subject=Website Email:">' + addr + '</a>');