If the popup.aspx page (the page holding the RapidSpellWeb control) is hosted on a different subdomain than the page that is being spell checked, then it will be necessary to add some document.domain calls in Javascript to allow the script to run across the subdomains. For example consider the situation where the popup.aspx runs under spell.host.tld, and the page is at host.tld
In the user page call the following Javascript (after the RapidSpell script import).
<script type='text/javascript'> document.domain = 'host.tld'; rapidSpell.dialog_documentDomain = 'host.tld'; </script>
In both the blank.html file (under the scripts folder) and also the popup.aspx, located on spell.host.tld, add
<script type='text/javascript'> document.domain = 'host.tld'; </script>
That should be all that is required, if you experience any difficulty please email support @ keyoti.com
Tip:
Content loading in iframes on the page (outside of the spell checker) will need to declare the same document.domain as the parent page. If an iframe does not initially load a page (or loads about:blank) try having it load a blank HTML page with document.domain set inside).