diff --git a/src/errors/handler.ts b/src/errors/handler.ts
index 58365ae..fd2681b 100644
--- a/src/errors/handler.ts
+++ b/src/errors/handler.ts
@@ -1,5 +1,5 @@
 import { FastifyReply, FastifyRequest } from "fastify";
-import { NotHtmlMimetypeError } from "./main";
+import { EngineParseError, IFastifyValidationError, InvalidParameterError, LocalResourceError, NotHtmlMimetypeError } from "./main";
 
 export default function errorHandler(
   error: Error,
@@ -8,7 +8,28 @@ export default function errorHandler(
 ) {
   if (error instanceof NotHtmlMimetypeError) {
     return reply.redirect(301, error.url);
+  } else if (error instanceof EngineParseError) {
+    return reply.code(500).view("/templates/error.ejs", {
+      title: "parse error",
+      description: "Engine can not parse the HTML page received from the remote server.",
+    });
+  } else if (
+    error instanceof InvalidParameterError ||
+    (
+      error as unknown as IFastifyValidationError
+    )?.statusCode === 400
+  ) {
+    return reply.code(400).view("/templates/error.ejs", {
+      title: "invalid parameter",
+      description: `Specified parameters are invalid.`,
+    });
+  } else if (error instanceof LocalResourceError) {
+    return reply.code(403).view("/templates/error.ejs", {
+      title: "local resource",
+      description: "Proxying local resources is forbidden.",
+    });
   } else {
+    console.log(error);
     return error;
   }
 }
diff --git a/src/errors/main.ts b/src/errors/main.ts
index bd528bd..07893e6 100644
--- a/src/errors/main.ts
+++ b/src/errors/main.ts
@@ -1,10 +1,17 @@
 export class EngineParseError extends Error {}
 export class InvalidParameterError extends Error {}
 export class LocalResourceError extends Error {}
+
 export class NotHtmlMimetypeError extends Error {
   url: string;
-  constructor(params: { url: string }) {
+  constructor(url: string) {
     super();
-    this.url = params?.url;
+    this.url = url;
   }
 }
+
+export interface IFastifyValidationError {
+  statusCode: number;
+  code: string;
+  validation: any;
+}
diff --git a/src/handlers/main.ts b/src/handlers/main.ts
index 0fbb172..27863d9 100644
--- a/src/handlers/main.ts
+++ b/src/handlers/main.ts
@@ -29,14 +29,14 @@ export default async function handlePage(
   }
 
   if (engine && engineList.indexOf(engine) === -1) {
-    throw new InvalidParameterError("Invalid engine");
+    throw new InvalidParameterError("engine");
   }
 
   const response = await axios.get(url);
   const mime: string | undefined = response.headers["content-type"]?.toString();
 
   if (mime && mime.indexOf("text/html") === -1) {
-    throw new NotHtmlMimetypeError({ url });
+    throw new NotHtmlMimetypeError(url);
   }
 
   const window = new JSDOM(response.data, { url }).window;
diff --git a/src/types/requests.ts b/src/types/requests.ts
index e395149..37271f9 100644
--- a/src/types/requests.ts
+++ b/src/types/requests.ts
@@ -3,11 +3,7 @@ import { handlerSchema } from "../handlers/handler.interface";
 import { engineList } from "../handlers/main";
 
 export type GetRequest = FastifyRequest<{
-  Querystring: {
-    url: string;
-    format?: string;
-    engine?: string;
-  };
+  Querystring: IGetQuery;
 }>;
 
 export interface IGetQuery {