Initially, its shares had climbed on the news that full-year pre-tax profits had grown 8% to £20.7m. However, investors began to lose faith as news trickled down that advertising had slowed as much as 9% in April and May.
In a conference call, Patrick Taylor, deputy chief executive, said, "It is one of the most volatile markets in 10 years. Up until the end of March, I think we were showing good signs of growth, but since then it has been more difficult."
He added that local advertising is faring better than national advertising.
The group's shares were trading at 420p at 3.36pm yesterday, down 22p on the previous day's close.