LONDON -- What a week it's been for the FTSE 100 (INDEX: ^FTSE)! First it soared to levels not seen since the dot-com madness, hitting a 13-year high of 6,876 points on Wednesday. Then on Thursday, the index of the U.K.'s top stocks suffered its biggest fall of the year, dropping 143 points (2.1%) to 6,697, after disappointing economic figures from China and on fears of a relaxing of the Federal Reserve's economic stimulus. Overall, the FTSE 100 ended the week down 69 points at 6,654 -- but it's still gained around 27% over the past 12 months. Here are three of the week's big gains, and one loss.

Marks & Spencer (MKS -0.78%)
Marks & Spencer, the High Street department store, had another good week, picking up 24 pence (5.3%) to 475 pence, to follow on from a 7.3% rise the previous week. Full-year pre-tax profit did fall by 14% to 564 million pounds, but that was pretty much expected -- and group sales were up 1.3% to 10 billion pounds. There will be further costs next year as the company revamps its online sales channels, but according to CEO Marc Bolland, "Three of the four parts of the business made strong progress." The trick now is to repeat that feat for general merchandise.

easyJet (EZJ 1.04%)
It's not often that airlines see their stock prices gain 150% in a year, but that's what has happened to budget short-haul operator easyJet over the past 12 months. Earlier in the month, the company reported good figures for its traditionally loss-making winter half, with the loss cut by 45% to 61 million pounds -- and that gave the price a nice boost. And this week we heard that easyJet is to buy 25 pairs of arrival and departure slots at Gatwick Airport from rival Flybe Group for 20 million pounds. The easyJet price ended the week 62 pence (5.2%) up on 1,250 pence.

Burberry (BRBY 1.11%)
Record annual sales and profits helped send Burberry's price up 62 pence (4.3%) to end the week at 1,518 pence. The purveyor of high-end fashion recorded an 8% rise in sales to 2 billion pounds, with a large part of that jump coming from rising retail sales in China. In fact, nearly 40% of the company's sales now come from the Asia-Pacific region. Burberry did face an exceptional charge of 83 million pounds from the termination of a fragrance license, but it still enjoyed record pre-tax profit of 428 million pounds, up 14%.

ARM Holdings (ARM)
The price of chip designer ARM Holdings has been soaring all year, achieving a 52-week gain of more than 120% by last week. But when Thursday's FTSE reversal kicked in, ARM's trailing P/E of nearly 70 appeared to spook some investors, and the price promptly slumped -- it ended the week 102 pence (9.4%) down at 986 pence. When bull runs falter, it does tend to be highly valued growth stocks that suffer, and that's what happened this week. But then, if you've held ARM stock for a year, you've still doubled your money.

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