when should equity and available for sale investments be in the profit and loss

Mike please explain to me when should equity investments or available for sale investments be in the profit or loss rather than in the comprehensive income section. This totally confuses me, using the past papers it is not clear at all for at times they do come in the profit or loss section and at other times they do come in the comprehensive income section. Although the total comprehensive income figure will be the same either way the profit for the year figure will be different which will be a mark or two missed. please explain