When I ran a site through http://validator.w3.org STRICT it failed on some items caused by simplesearch, namely
GET in uppercase
fields not wrapped in anything, like <fieldset>
I’ve got round this by writing my own chunk but is there an underlying philosophy that everything should be developed to comply with <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">