Setting up responsive image in WordPress

functions.php

<?php
add_filter( 'post_thumbnail_html', 'remove_thumbnail_dimensions', 10 ); 
add_filter( 'image_send_to_editor', 'remove_thumbnail_dimensions', 10 );
function remove_thumbnail_dimensions( $html ) 
{ 
 $html = preg_replace( '/(width|height)="d*"s/', "", $html ); 
 return $html;
}
?>

style.css

/* Images */ 
.entry-content img, 
.comment-content img, 
.widget img { 
 max-width: 97.5%; 
} 
img[class*="align"], 
img[class*="wp-image-"] { 
 height: auto; 
} 
img.size-full { 
 max-width: 97.5%; 
 width: auto; 
}
// Caption
.wp-caption, 
.wp-caption-text { 
 max-width: 97.5%; 
 height: auto; 
 width: auto9; /* ie8 */ 
}