By Rupert Hargreaves S4Capital, the digital advertising, marketing and technology services company founded by Sir Martin Sorrell, has reported another slowdown in revenue amid continued client caution in the advertising market. For the first quarter, the company reported a like-for-like net revenue decline of 11.7 per cent. On a reported basis, revenue declined 14.9 per cent. The company said the decline reflected “continuing client caution” and an anticipated “reduction in technology activity services.” Its technology services division reported the most significant decline, with net revenue f…