Be sure you are using the Marketo supplied blank template.
When using their blank template, setting up landing page formatting that works consistently can be tricky. Is a knowledgeable HTML person creating the code and/or are you using a web page design program like Adobe Dreamweaver? Are you using CSS? You can tell if the top your landing page's HTML element has something that looks like the following:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>
Add your page title here</title>
<link rel="stylesheet" href="http://.../screen.css" type="text/css" media="screen, projection">
<link rel="stylesheet" href="http://...print.css" type="text/css" media="print">
<!--[if lt IE 8]><link rel="stylesheet" href="http://...ie.css" type="text/css" media="screen, projection"><![endif]-->
<link rel="stylesheet" href="http://...v6.css" type="text/css" media="screen, projection">
<link rel="stylesheet" href="http://...query-ui-1.8.4.custom.css" type="text/css" media="screen, projection">
</head>
If not, this may be contributing to the problem.
Also,
if you have multiple HTML elements, the order in which they are downloaded, relative to other page elements, is based on its Layer. Your custom HTML should be on a higher-numbered layer than other elements. See the Add Custom HTML to a Landing Page tutorial for more info.
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