Depending on your website's content, your spelling and grammar can have a great effect on how reliable your visitors perceive it to be. Bad grammar can make it difficult for readers to understand your original thoughts and intentions and the main point of your work could very much be missed. Also, if you have a bunch of spelling errors and the grammar just doesn't make sense, surfers may conclude that the person who wrote the content is uneducated, which reduces your credibility and thus, the chance of return traffic.
Spellcheckers are strongly suggested if you want to somewhat ensure that you get your point across to your audience. However, most programs only check the spelling of words and not necessarily the order in which they occur or rather, the grammar. Often, words such as "there" and "their" or "it's" and "its" are confused and although they are spelled correctly, they create obscure sentences. In cases where words are used incorrectly, you would need a grammar checker as well. Because the technology of grammar software far exceeds that of spellcheckers, you won't find many that are free, but if you have a copy of Word you'll be happy to know that a grammar checker is part of the software.
In HTML mode, SpellOnline knows how to parse the HTML code and correct only the relevant text, while the HTML tags remain clearly visible. This feature is a time saver for people writing web pages. Their database contains more words than most spellcheckers including proper names from all categories (famous people, politicians, first names, etc.), country names, city names, company names and more.
This program is a free Internet Explorer browser extension that spell checks text input boxes on a webpage. It should come in particularly handy for users who do a lot of web-based text entry (e.g. web mails, forums, blogs, diaries). Even if your web application already includes spellchecking functionality, you might still want to install this utility because it is definitely much faster than a server-side solution. Plus you get to store and use your personal word list across all your applications, instead of maintaining separate ones on each application.
Not as sophisticated at those listed above, this spellchecker is easy to use allowing you to either check the spelling of one word or copy and paste a paragraph that you want checked. It also gives you the word and character count.
SiteCheck from SiteOwner
While this tool doesn't let you check individual paragraphs if gives you the possibility to check your entire site by only specifying the URL. This is a fast and easy way to spellcheck your entire site in one go.