I have an online app that I am wanting to validate the HTML markup of against the W3C validator.
Problem is users need to log in first to access them.
How do I go about validating these pages?
With this html validator extension. Or by Ctrl-U, copy-paste into the w3c page.
You have to run the service they provide on your server:
http://validator.w3.org/docs/install.html
Thats what we've done, works great.
I think it's best practice to be validating your sites source when it's in development not when its in production... Treat this just like running unit tests. You shouldn't have markup errors go live either.
Assuming you mean markup validation, log in yourself, go to the page you want, view source, and use the direct input option.
I assume you mean w3 validator service. You can copy paste the html contents into the validator or save the html into a file and upload it. If you have Firefox Web developer extension, it provides a 'validate local HTML' option.
OmniValidator for Firefox:
Omnivalidator sends the content of the currently visible page to one or more validation services configured in the extension preferences. These validators may be publicly hosted (the defaults are the publicly hosted W3C Markup Validator and Validator.nu) or hosted locally. The results are retrieved from the validators, parsed, and displayed in a collapsable error display panel and summarized with an icon and tooltip on the Omnivalidator button, which can be placed on a browser toolbar. Validation is initiated either by clicking on the Omnivalidator button or by configuring URLs which are automatically validated with one or more validators in the extension preferences.
来源：https://stackoverflow.com/questions/2052580/validate-markup-of-password-protected-sites-with-w3c