diff --git a/homepage/static/assets/js/captcha_refresh.js b/homepage/static/assets/js/captcha_refresh.js
index f3bee68..bc5f1d9 100644
--- a/homepage/static/assets/js/captcha_refresh.js
+++ b/homepage/static/assets/js/captcha_refresh.js
@@ -17,8 +17,8 @@ const captcha_span = document.getElementsByClassName("captcha")[0];
 const captcha_img = captcha_span.children[1];
 
 captcha_span.classList.toggle("refresh");
-captcha_span.children[3].innerHTML
-    = `<button id="refresh">Refresh</button>ed in <b><span id="remain">600</span></b> seconds.`;
+captcha_span.children[3].innerHTML =
+    `<button id="refresh">Refresh</button>ed in <b><span id="remain">600</span></b> seconds.`;
 
 const captcha_refresh = document.getElementById("refresh");
 const captcha_remain = document.getElementById("remain");
@@ -27,13 +27,15 @@ captcha_refresh.classList.toggle("refresh");
 captcha_refresh.addEventListener("click", async e => {
     e.preventDefault();
     captcha_refresh.disabled = true;
-    // Checking if CAPTCHA is solved deletes it.
     setTimeout(async () => {
         captcha_refresh.disabled = false;
         await fetch(`/captcha/${g_current_captcha_id}`); }, 3000);
     await getNewCaptcha();
 });
 
+// Remove unused CAPTCHA on a server.
+window.addEventListener("unload", () => fetch(`/captcha/${g_current_captcha_id}`));
+
 setInterval(async () => {
     captcha_remain.innerText = --g_captcha_timeout_remain;
     if (g_captcha_timeout_remain == 0)