diff --git a/src/common/content_scripts.js b/src/common/content_scripts.js
new file mode 100644
index 0000000..7186037
--- /dev/null
+++ b/src/common/content_scripts.js
@@ -0,0 +1,22 @@
+function injectStylesheet(stylesheetName) {
+  var link = document.createElement('link');
+  link.setAttribute('rel', 'stylesheet');
+  link.setAttribute('href', stylesheetName);
+  document.head.appendChild(link);
+}
+
+function injectStyles(css) {
+  injectStylesheet('data:text/css;charset=UTF-8,' + encodeURIComponent(css));
+}
+
+function injectScript(scriptName) {
+  var script = document.createElement('script');
+  script.src = scriptName;
+  document.head.appendChild(script);
+}
+
+function escapeUsername(username) {
+  var quoteRegex = /"/g;
+  var commentRegex = /<!---->/g;
+  return username.replace(quoteRegex, '\\"').replace(commentRegex, '');
+}