Fix mistakes in the Custom Server doc (#9930)

Author: cullylarson

docs/advanced-features/custom-server.md

@@ -17,7 +17,7 @@ description: Start a Next.js app programmatically using a custom server.
 
 Typically you start your next server with `next start`. It's possible, however, to start a server 100% programmatically in order to use custom route patterns.
 
-> Before deciding to use a custom a custom server please keep in mind that it should only be used when the integrated router of Next.js can't meet your app requirements. A custom server will remove important performance optimizations, like **serverless functions** and **[Automatic Static Optimization](/docs/advanced-features/automatic-static-optimization.md).**
+> Before deciding to use a custom server please keep in mind that it should only be used when the integrated router of Next.js can't meet your app requirements. A custom server will remove important performance optimizations, like **serverless functions** and **[Automatic Static Optimization](/docs/advanced-features/automatic-static-optimization.md).**
 
 Take a look at the following example of a custom server:
 
@@ -75,7 +75,7 @@ const app = next({})
 
 The above `next` import is a function that receives an object with the following options:
 
-- `dev`: `Boolean` - Whether or not to launch Next.js in dev mode. Defaults `false`
+- `dev`: `Boolean` - Whether or not to launch Next.js in dev mode. Defaults to `false`
 - `dir`: `String` - Location of the Next.js project. Defaults to `'.'`
 - `quiet`: `Boolean` - Hide error messages containing server information. Defaults to `false`
 - `conf`: `object` - The same object you would use in [next.config.js](/docs/api-reference/next.config.js/introduction.md). Defaults to `{}`
@@ -86,7 +86,7 @@ The returned `app` can then be used to let Next.js handle requests as required.
 
 By default, `Next` will serve each file in the `pages` folder under a pathname matching the filename. If your project uses a custom server, this behavior may result in the same content being served from multiple paths, which can present problems with SEO and UX.
 
-To disable this behavior & prevent routing based on files in `pages`, open `next.config.js` and disable the `useFileSystemPublicRoutes` config:
+To disable this behavior and prevent routing based on files in `pages`, open `next.config.js` and disable the `useFileSystemPublicRoutes` config:
 
 ```js
 module.exports = {