style.css in Wordpress doesn't work after adding header.php file -

if add simple "header.php" file theme folder, style.css stops working, if delete "header.php", starts working again.

how can resolve this?

here's simple code of files:

index.php:

<?php  get_header();   ?>  <p>test</p>   <button id="btn">jquery test</button> 

style.css:

    /* theme name: thème dias description: mon thème */      p{     color:green;     font-size:100px;     } 

functions.php

<?php //definir le répertoire du thème define("theme_dir", get_template_directory_uri());  //enlever le générateur de tags meta pour la sécurité (les gents ne peuvent pas voir quelle version wp) remove_action('wp_head', 'wp_generator');   // enqueue styles function enqueue_styles() {      /* main css */     wp_register_style( 'main-css', theme_dir . '/style.css', array(), '1', 'false');     wp_enqueue_style( 'main-css' );  } add_action( 'wp_enqueue_scripts', 'enqueue_styles' );   // enqueue scripts function enqueue_scripts() {     wp_enqueue_script( 'jquery' );      /* jquery custom scripts */     wp_register_script( 'jquery-custom', theme_dir . '/js/custom.js', array('jquery'), '1.0.0', 'true');     wp_enqueue_script( 'jquery-custom' );  } add_action( 'wp_enqueue_scripts', 'enqueue_scripts' ); ?> 

header.php

<?php wp_head(); ?> 

thank you!

your header.php , index.php good, need replace following line of functions.php file:

wp_register_style( 'main-css', theme_dir . '/style.css', array(), '1', 'false'); 

with one:

wp_register_style( 'main-css', theme_dir . '/style.css', array(), '1', 'all'); 

and good.