modtime:          htmlModTime,
			reqHeader: map[string]string{
				"If-Modified-Since": htmlModTime.UTC().Format(TimeFormat),
			},
			wantStatus: 304,
		},
		"not_modified_etag": {
			file:      "testdata/style.css",
			serveETag: `"foo"`,
			reqHeader: map[string]string{
				"If-None-Match": `"foo"`,
			},
			wantStatus: 304,
		},
		"not_modified_etag_no_seek": {