I would like to begin by asking that you post your questions in the most relevant forum section as this lets the people involved in that matter see it. I have moved the thread to the RadSpell for ASP.NET AJAX forums already, because I assumed this is the product you are using, considering you mention spell popups.
To answer the concrete question—RadSpell always works through a dialog and does not offer inline spell checking. This is a feature all modern browsers have, however, and you can control it via the spellcheck HTML5 attribute: https://developer.mozilla.org/en-US/docs/Mozilla/Tech/XUL/Attribute/spellcheck.
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