diff --git a/src/css3/cssom/cssrule.rs b/src/css3/cssom/cssrule.rs
new file mode 100644
index 000000000..8556b7cdc
--- /dev/null
+++ b/src/css3/cssom/cssrule.rs
@@ -0,0 +1,62 @@
+pub enum CssRuleType {
+    UnknownRule = 0,
+    StyleRule = 1,
+    CharsetRule = 2,        // Obsolete
+    ImportRule = 3,
+    MediaRule = 4,
+    FontFaceRule = 5,
+    PageRule = 6,
+    KeyframesRule = 7,
+    KeyframeRule = 8,
+    MarginRule = 9,         // Obsolete
+    NamespaceRule = 10,
+    CounterStyleRule = 11,
+    SupportsRule = 12,
+    DocumentRule = 13,      // Obsolete
+    FontFeatureValuesRule = 14,
+    ViewportRule = 15,      // Obsolete
+    RegionStyleRule = 16,   // Obsolete
+}
+
+pub struct CssStyleRule {
+}
+
+pub enum CssTypeRuleType {
+    StyleRule(CssStyleRule),
+    CharsetRule(CssCharsetRule),
+    ImportRule(CssImportRule),
+    MediaRule(CssMediaRule),
+    FontFaceRule(CssFontFaceRule),
+    PageRule(CssPageRule),
+    KeyframesRule(CssKeyframesRule),
+    KeyframeRule(CssKeyframeRule),
+    MarginRule(CssMarginRule),
+    NamespaceRule(CssNamespaceRule),
+    CounterStyleRule(CssCounterStyleRule),
+    SupportsRule(CssSupportsRule),
+    DocumentRule(CssDocumentRule),
+    FontFeatureValuesRule(CssFontFeatureValuesRule),
+    ViewportRule(CssViewportRule),
+    RegionStyleRule(CssRegionStyleRule),
+}
+
+struct CssRule {
+    text: String,
+    parent_rule: Option<Rc<CssRule>>,
+    parent_stylesheet: Option<Rc<CSSStyleSheet>>,
+    type_: CssRuleType,
+}
+
+struct CssGroupingRule {
+    css_rules: CssRuleList,
+}
+
+impl CssGroupingRule {
+    pub fn delete_rule(&mut self, idx: usize) {
+        self.css_rules.remove(idx);
+    }
+
+    pub fn insert_rule(&mut self, idx: usize, rule: CssRule) {
+        self.css_rules.insert(idx, rule);
+    }
+}
\ No newline at end of file
diff --git a/src/css3/cssom/cssrule_list.rs b/src/css3/cssom/cssrule_list.rs
new file mode 100644
index 000000000..43f5868fe
--- /dev/null
+++ b/src/css3/cssom/cssrule_list.rs
@@ -0,0 +1,11 @@
+type CssRuleList = vec<CssRule>;
+
+impl CssRuleList {
+    fn item(&self, idx: usize) -> Option<&CssRule> {
+        self.get(idx)
+    }
+
+    fn length(&self) -> usize {
+        self.len()
+    }
+}
\ No newline at end of file
diff --git a/src/css3/cssom/stylesheet.rs b/src/css3/cssom/stylesheet.rs
new file mode 100644
index 000000000..9d4b8bdb4
--- /dev/null
+++ b/src/css3/cssom/stylesheet.rs
@@ -0,0 +1,32 @@
+struct CSSStyleSheet {
+    rules: CssRuleList
+}
+
+impl CSSStyleSheet {
+    pub fn new() -> Self {
+        Self {
+            rules: vec![]
+        }
+    }
+
+    pub fn delete_rule(&mut self, idx: usize) {
+        self.rules.remove(idx);
+    }
+
+    pub fn insert_rule(&mut self, idx: usize, rule: CssRule) {
+        self.rules.insert(idx, rule);
+    }
+
+    pub fn replace_async(&mut self, idx: usize, rule: CssRule) {
+        self.rules[idx] = rule;
+    }
+
+    pub fn replace(&mut self, idx: usize, rule: CssRule) {
+        self.rules[idx] = rule;
+    }
+
+    // CSSOM:
+    //   property: rules obsolete
+    //   method: addRule() obsolete
+    //   method: removeRule() obsolete
+}
\ No newline at end of file
diff --git a/src/css3/cssom/stylesheet_list.rs b/src/css3/cssom/stylesheet_list.rs
new file mode 100644
index 000000000..24f6450a2
--- /dev/null
+++ b/src/css3/cssom/stylesheet_list.rs
@@ -0,0 +1,3 @@
+struct StyleSheetList {
+    item: vec<StyleSheet>
+}
\ No newline at end of file