space between lines

Hi, Yesterday evening I wanted to add a page to toerfietsleusden.nl. The space between lines has been changed from one to two spaces between the lines. If I use text in stead of visual mode text occurs normal. If I add text in visual mode, there is a double space between lines. I tried it with different laptops and different browser, all the same effect. How can I correct that. Kind regards Hans Hagmeijer