If you go to the "Install Ad Code" page for the zone in your Publishers Dashboard, you will want to make sure that the "Vertical" checkbox is UNCHECKED under "Advanced Settings" on that page.
You will also want to make sure that the "Anchor Style" field contains "float:left;" so that the ads will float to the left. After you UNCHECK the "Vertical" option and then click on "Save", the system should automatically add the 'float:left' property back to the "Anchor Style" field. If you do not see the 'float:left' property in that field, you will want to manually add it to the field.
You should also check to ensure that your website's div that holds your ads is wide enough to hold the floated ads, even with their margins calculated. The total pixel width of the floated ads plus their margins should equal a width of less than the div that encompasses those ads on your site. If not, the ads will not float as they should and will be pushed down vertically due to the div not being wide enough to hold them.
If you need further assistance with the display of your ads, please open a support ticket so we can help.
We tend to answer most support tickets during normal business hours: Monday to Friday, 9:00 am to 6:00 pm (EST). However, we're constantly monitoring tickets, and we'll address urgent issues on nights and weekends, too.Open a Ticket