Look at the error message and your code:
Unmatched '}' in C:\xampp\htdocs\new folder\registration.php on line 88
echo "<div class='form'>
<h3>Username/password is incorrect.</h3>
<br/>Click here to <a href='login.php'>Login</a></div>";
That doesn't mean it has to be a missing "}", it can means it's an extra "}".
So why are there two "}" immediately before the
You should expect to get syntax errors every day, probably many times a day while you are coding - we all do regardless of how much experience we have! Sometimes, we misspell a variable, or a keyword; sometimes we forget to close a string or a code block. Sometimes the cat walks over your keyboard and types something really weird. Sometimes we just forget how many parameters a method call needs.
We all make mistakes.
And because we all do it, we all have to fix syntax errors - and it's a lot quicker to learn how and fix them yourself than to wait for someone else to fix them for you! So invest a little time in learning how to read error messages, and how to interpret your code as written in the light of what the compiler is telling you is wrong - it really is trying to be helpful!
So read this: How to Write Code to Solve a Problem, A Beginner's Guide Part 2: Syntax Errors
] - it should help you next time you get a compilation error!