new file mode 100644
--- /dev/null
+++ b/src/http/modules/ngx_http_not_modified_filter.c
@@ -0,0 +1,74 @@
+
+#include <ngx_config.h>
+#include <ngx_core.h>
+#include <ngx_http.h>
+
+
+
+static int ngx_http_not_modified_filter_init(ngx_cycle_t *cycle);
+
+
+static ngx_http_module_t  ngx_http_not_modified_filter_module_ctx = {
+    NULL,                                  /* create main configuration */
+    NULL,                                  /* init main configuration */
+
+    NULL,                                  /* create server configuration */
+    NULL,                                  /* merge server configuration */
+
+    NULL,                                  /* create location configuration */
+    NULL                                   /* merge location configuration */
+};
+
+
+ngx_module_t  ngx_http_not_modified_filter_module = {
+    NGX_MODULE,
+    &ngx_http_not_modified_filter_module_ctx, /* module context */
+    NULL,                                  /* module directives */
+    NGX_HTTP_MODULE,                       /* module type */
+    ngx_http_not_modified_filter_init,     /* init module */
+    NULL                                   /* init child */
+};
+
+
+static int (*next_header_filter) (ngx_http_request_t *r);
+
+
+static int ngx_http_not_modified_header_filter(ngx_http_request_t *r)
+{
+    time_t  ims;
+
+    if (r->headers_out.status != NGX_HTTP_OK
+        || r->headers_in.if_modified_since == NULL
+        || r->headers_out.last_modified_time == NULL)
+    {
+        return next_header_filter(r);
+    }
+
+    ims = ngx_http_parse_time(r->headers_in.if_modified_since->value.data,
+                              r->headers_in.if_modified_since->value.len);
+    
+    ngx_log_debug(r->connection->log, "%d %d" _
+                  ims _ r->headers_out.last_modified_time);
+
+    /* I think that the date equality is correcter */
+
+    if (ims != NGX_ERROR && ims == r->headers_out.last_modified_time) {
+        r->headers_out.status = NGX_HTTP_NOT_MODIFIED;
+        r->headers_out.content_length = -1;
+        r->headers_out.content_type->key.len = 0;
+        r->headers_out.content_type = NULL;
+
+        /* TODO: delete "Accept-Ranges" header
+    }
+
+    return next_header_filter(r);
+}
+
+
+static int ngx_http_not_modified_filter_init(ngx_cycle_t *cycle)
+{
+    next_header_filter = ngx_http_top_header_filter;
+    ngx_http_top_header_filter = ngx_http_not_modified_header_filter;
+
+    return NGX_OK;
+}