W3cValidate.vim is a plugin that enables buffer/url validation using the http://validator.w3.org api
Copy w3cvalidate.vim file inside plugin directory, source it or restart Vim. Use
:W3cValidate to validate the current buffer
:W3cValidate "[url_here]" to validate a hosted page
:W3cValidateDT "[doctype]" to validate the buffer using the [doctype] override. Make sure the doctype is a valid doctype
The validator service url can be changed if you run an instance of it localy by setting g:w3_validator_url in .vimrc
The script has API timeout default to 20 seconds. You can change it by setting g:w3_apicall_timeout in .vimrc
Needs vim compiled with +python option. Works out of the box on Ubuntu and Ubuntu-derivates.