ASOS, the online fashion retailer, enjoyed a good Christmas with both sales and margins strong and growth both in the UK and abroad, though sales growth did slow from earlier in the year.Sales rose 30% year on year in the 5 weeks to 3 January and were up by 38% for the 42 weeks to 17 January. UK sales rose by 25% and international by 102% over the 42-week period. Gross margin rose by 80 basis points for the 5 weeks to 3 January 2010, while active customers rose by 25% to 1.5m.Last November, ASOS reported total sales for 7 weeks to 15 November were up 46% year-on-year with UK sales 23% ahead and international sales up by 161%, suggesting a slight slow down recently in recent weeks, though the firm remains upbeat."I am pleased to report another excellent Christmas for ASOS. Sales and margin were both strong and we exited the Christmas period with a clean stock position. We continue to trade in line with the board's expectation and remain confident for the outcome for the full year," Nick Robertson, chief executive, said.ASOS saw strong demand 'party wear' over Christmas, particularly in clothing including lace, while Ugg boots were also big sellers as the snow hit. The cold weather had a mixed impact on the group. While the freeze meant customers were at home more, it also meant the company struggled to get items delivered. The group will launch a US-specific site later in 2010 and has identified the US as a key market going forward. The company is on track to achieve a sales target of £230m this year, up from £165m last year. Prior to Monday's update analysts were forecasting a consensus pre-tax profit for the year to end-March 2010 of £20m, up from 14.1m in the previous year. Broker Charles Stanley did not like the update. It reiterated its 'sell' stance, adding that the current share price demands continuous upgrades to consensus estimates and this latest statement 'did not deliver one'.