The email would include the tokens to build the URL such as http://www.example.com/?CompanyName={{company.Company Name:default=MyCompanyName}}&AccountNumber={{company.SFDC Account Num:default=000000}}
JavaScript/jQuery can capture the URL parameters and pre-populate the fields in the non-Marketo landiong page.
It would be something like:
<s c r i p t language="Javascript" src="/js/public/jquery-latest.min.js" type="text/javascript"></s c r i pt>
<s c r i p t src="/js/public/jQueryString-2.0.2-Min.js" type="text/javascript" ></s c r i p t>
<s c r i p t >
var $jQ = jQuery.noConflict();
var pCompanyName = $jQ.getQueryString({ ID: "CompanyName" });
var pAccountNumber = $jQ.getQueryString({ ID: "AccountNumber" });
document.getElementById("CompanyName").setAttribute("value", pCompanyName);
document.getElementById("AccountNumber").setAttribute("value", pAccountNumber);
</s c r i p t>
*** Please note "script" is a single word without spaces. I have separated to avoid the system interpreting as a real tag. ***