JavaScript Spell Check is a component that lets you add an orthographic corrector for forms and text boxes to webpages.
JavaScript Spell Check gives you 3 powerful characteristics:
1. A popup window, similar to MS Word, to test the webpage orthography, ideal for testing forms and data entry.
2. Ajax Spellcheck, a powerful API to develop your own orthography checking applications in Ajax.
3. A new Spellcheck function to add to JavaScript.
It is compatible with storages based on Windows servers, simply upload it and it´s ready to use on your web projects.
You can download dictionaries, like a Spanish one, here
Here