'jQuery spellcheck' is the industry leading spellchecker plugin for jQuery flavor JavaScript from javascript-spellcheck.com.
The spellcheck plugin can also be used to spellcheck rich/wysiwyg HTML Editors such as TinyMCE and CKEditor. JQuery spell check can also be used in 'abstract' as a behind-the-scenes spell-checker for form-processing or online word games.
JQuery spell check is unique in that it does all of the spell checking its self. It runs using AJAX behind teh scenes to avoid users having to download huge dictionary files. We have AJAX handlers for ASP VBScriupt, PHP, ASP.Net (C# and VB.Net...) and Java. Unlike other plugins we never send your data across the Internet for remote processing on a 3rd party server. This makes jQUery spell-check ideal for use in an Intarnet or secure login environment. It can be installed on Windows, Linux and OSX just by uploading 1 folder into your website project. YOu can read the full guide at http://www.javascriptspellcheck.com/jquery-spell-check/#tabs-3
Users can also 'Add' or 'Learn' words just lke in Microsoft Word. These words are stored locally and affect only 1 user. With advanced setup ( http://www.javascriptspellcheck.com/JavaScript_SpellChecking_Dictionaries ) the developer can also cause those words to be added to a central repository for all users to share. This is very popular on Medical and Engineering intarnet projects.