Forgot to check SEO for landing pages? Interns or beginners who might not know what tools to use? Freelancers that did not check SEO before they delivered their landing pages?

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 a client-side script that checks HTML source code and detects violations of a defined coding standard.

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.

SimplyTestable is an online markup validation services that saves your time and allows you validate the HTML markup for your entire site in one click.  It takes the pain out of routine front-end web testing.

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

The official W3C validator does not yet provide a way to submit several URLs at once. So, if you want to check your whole website, you need to submit each of your URLs individually, which is a slow process. W3Clove provide a simpler, faster way to submit several pages at once.

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.

ht5ifv is an extensible and highly configurable jQuery HTML5 form validation plugin is an which allows validation of the HTML5′s forms while the user is typing.

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.

jFormer is a complete framework for generating template based forms for websites, blogs etc. With this simple and manageable framework, you can create forms that can use triggers to lock/unlock fields, prevent bot intervention (no CAPTCHA required), and can be paused and resumed.

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.

VM FormValidator is a JavaScript form validation script based on MooTools. It aims to provide simple, reliable validation for all form element types across all browsers in an unobtrusive manner.

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.

QapTcha is a simple jQuery captcha plugin built using jQuery UI. To unlock a form, the user has to drag a slider from the left to the right. This is a bulletproof captcha plugin because bots aren’t able to perform drag and drop events.

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.

bValidator is a jQuery validation plug-in for client side form validation. It supports fully customized error messages defined with template and CSS.

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…

jQuery.validVal is an open source validation plugin designed to simplify form validation. It is highly customizable, very feature rich and can easily be dropped on any type of HTML-form (even AJAX-forms) with very little effort.

validVal supports three default value-validations: required, numeric and email-format. It supplies a workaround for IE’s lack of support for the :focus-pseudoclass.