After The Deadline is a project of Automattic (the creator of Wordpress) which checks:

spelling
grammar
styles (finds complex phrases, cliches, bias-language & suggests simple ones)
and detects misused words (has a database of 1500 most misued words & suggestions)

The software used to come as a plugin for several projects (like Wordpress, RoundCube, PHP List) [...]

First impressions are important & a website with lots of typo may easily result in losing visitors.
Spell Check Rex is an open source website spell checking application, built with PHP & MySQL, which can be installed on any website to automatically monitor & report spelling mistakes.

The application spiders the given website and generates reports. It [...]

In this post I want to suggest you five interesting and free spell checkers for HTML Forms (input and text area) ready to use in your web projects. I also provided some suggestions regarding how to implement them on your pages using a few lines of HTML and Javascript code. Try them!
Any suggestion about this [...]