I followed it and placed the styling markup in the Layout base page
<style type="text/css">
.x-form-type-text textarea.x-form-invalid-field, .x-form-type-text input.x-form-invalid-field, .x-form-type-password textarea.x-form-invalid-field, .x-form-type-password input.x-form-invalid-field, .x-form-type-number textarea.x-form-invalid-field, .x-form-type-number input.x-form-invalid-field, .x-form-type-email textarea.x-form-invalid-field, .x-form-type-email input.x-form-invalid-field, .x-form-type-search textarea.x-form-invalid-field, .x-form-type-search input.x-form-invalid-field, .x-form-type-tel textarea.x-form-invalid-field, .x-form-type-tel input.x-form-invalid-field {
background-color: #FFF;
background-repeat: repeat-x;
background-position: center bottom;
border-color: #C30;
}
</style>
but got both styling in the resulting page and image still there (this is from the page inspector) :
.x-form-type-text textarea.x-form-invalid-field, .x-form-type-text input.x-form-invalid-field, .x-form-type-password textarea.x-form-invalid-field, .x-form-type-password input.x-form-invalid-field, .x-form-type-number textarea.x-form-invalid-field, .x-form-type-number input.x-form-invalid-field, .x-form-type-email textarea.x-form-invalid-field, .x-form-type-email input.x-form-invalid-field, .x-form-type-search textarea.x-form-invalid-field, .x-form-type-search input.x-form-invalid-field, .x-form-type-tel textarea.x-form-invalid-field, .x-form-type-tel input.x-form-invalid-field {
background-color: #FFF;
background-repeat: repeat-x;
background-position: center bottom;
border-color: #C30;
}
.x-form-type-text textarea.x-form-invalid-field, .x-form-type-text input.x-form-invalid-field, .x-form-type-password textarea.x-form-invalid-field, .x-form-type-password input.x-form-invalid-field, .x-form-type-number textarea.x-form-invalid-field, .x-form-type-number input.x-form-invalid-field, .x-form-type-email textarea.x-form-invalid-field, .x-form-type-email input.x-form-invalid-field, .x-form-type-search textarea.x-form-invalid-field, .x-form-type-search input.x-form-invalid-field, .x-form-type-tel textarea.x-form-invalid-field, .x-form-type-tel input.x-form-invalid-field {
background-color: #FFF;
background-image: url("/extjs/resources/ext_theme_gray/images/grid/invalid_line-gif/ext.axd");
background-repeat: repeat-x;
background-position: center bottom;
border-color: #C30;
}