anchor.diff:      out "</tr>\n"
       out "<tr><th class='txt'>Function</th><th class=txt>Shape</th><th class=txt>Type</th><th class=txt>Device</th>"
       for _ in columns do 
  -        out "<th class='num lb'>Mean</th><th class='num'>StdDev</th>"
  +        out "<th class='num lb npr'>Mean</th><th class='num min'>StdDev</th>"
       out "</tr>\n"
   
       let funcs = bms |> Seq.map (fun bm -> bm.Method) |> Seq.distinct
  
positive.code:     out ".info {text-align: left; border: none; font-weight: normal; vertical-align: top; font-size: 80%%}\n"
      out "th.info {font-weight: bold;}\n"
      out "table.info {width: 230px}\n"
      out "</style>\n"
      out "</head><body>\n"
  
  
negative.code:             for id, _ in columns do
                  let mean, std = 
                      match libBms |> Seq.tryFind (fun bm -> bm.Lib = id) with
                      | Some bm -> sprintf "%.02f ms" bm.Mean, sprintf "&plusmn;%.02f ms" bm.StdDev
                      | None -> "&mdash;", "&mdash;"                   
                  out "<td class='num lb npr'>%s</td>" mean
                  out "<td class='num min'>%s</td>" std
              out "</tr>\n"                            
  
      out "</table>\n"    
  