Client side validation is not sufficient in any project because the javascript can be bypassed and people can submit requests directly to the server. However, that doesn’t mean client side validation should be forgotten. This library is for those who care about the user experience.

Inpage SEO Checker will continuously check basic SEO properties continuously  As soon as you violate a SEO check, an red one page error is shown – just like in unit testing. Inpage SEO Checker is easy to add to your page, just include one small JavaScript file and you’re ready to go.

The Inpage SEO Checker does basic onpage SEO checking. Number of H1,H2,H3 tags, checking for alt attributes on iMG tags, META description and keywords, page title and EM and STRONG tag usage.

HTML_CodeSniffer is written entirely in JavaScript, does not require any server-side processing and can be extended by developers to enforce custom coding standards by creating your own “sniffs”.

It can be used in two ways. Called directly in JavaScript source, HTML_CodeSniffer will provide a list of known and potential violations to the calling script. It also comes with a pop-up auditor interface, accessible via a bookmarklet, letting you browse through messages emitted from one of the defined standards. Where possible, the auditor also points you to the HTML element causing the problem.

HTML_CodeSniffer comes with a set of 3 standards that enforce the Web Content Accessibility Guidelines (WCAG) 2.0.

The service currently validates the HTML markup for the entire site (more features coming soon)

• Site-wide HTML markup validation in one click
• Overview report of your entire site’s successes and failures
• Detailed per-URL error report

W3Clove is a site-wide HTML markup validator. It allows you to check the validity of the markup of several pages from your website, and gives you a summary of the most common errors and warnings, with a single click.

It is extensible because it allows the programmer to define new restrictions beyond those already defined by HTML5.

It is highly configurable because not only does it allow changes to the validation rules defined by HTML5, but also the addition of new ones.

Fields in jFormer forms can be duplicated and based on pre-defined template. Forms can be validated on both client and server side. jFormer uses CSS for complete control on UI and supports AJAX to allow you to minimize callbacks to server side.

It is 100% style-able via CSS and allows for custom validations and error messages. Error messages can be displayed above the form, above each input, or below each input.

VMFormValidator should not be used as a replacement for server-side validation (using PHP, .NET, etc) because JavaScript can be disabled.

This intuitive jQuery captcha plugin makes things very easy for you with a limited amount of setup required and standard XHTML and CSS classes in place to make changing the appearance super easy.

This client side validation plugin comes with many validation functions like:

• Date validation
• Email validation
• URL and IP address
• Validation of dynamic forms
• Customized validation functions and more…