print('<html>')
     print('<style>')
     print('table, tr, th, td { border: 1px solid black; }')
-    print('tr:nth-child(7n+2) td { background-color: yellow; }')
+    print('.day_row:nth-child(7n+2) { background-color: yellow; }')
     print('</style>')
     print('<table>')
     print('<tr>')
     sorted_dates.reverse()
     sum_district = sorted_districts[-1]
     for date in sorted_dates:
-        print('<tr>')
+        print('<tr class="day_row">')
         print('<td>%s</td>' % date)
         long_wsum = translate['wsum']
         long_wavg = translate['wavg']