Bugs can occur due to mistakes made during coding, design flaws, or unexpected interactions between different software parts.

1). Syntax Error: A mistake in the code that violates the programming language's syntax rules. For example, forgetting to close a parenthesis or using an undefined variable.

Reason: A developer forgets to close an HTML tag, causing the entire webpage to display incorrectly.

2). Logic Error: A bug where the code produces unexpected results due to flawed logic. For example, a loop that doesn't terminate correctly.

Reason: A shopping cart on an e-commerce website fails to apply a discount correctly, resulting in incorrect pricing calculations.

3). Runtime Error: Occurs while the program is running and typically leads to the program crashing or freezing. Examples include division by zero or accessing an invalid memory location.

Reason: A JavaScript function encounters an error and stops executing, causing other dependent functions on the webpage to malfunction.

4). Null Pointer Exception: This occurs when a program tries to use a reference that points to null. For example, accessing a variable that hasn't been assigned a value.

Reason: A user submits a form on a website without filling in a required field, leading to a null value error on the server side.

5). Infinite Loop: A loop that doesn't terminate as intended, causing the program to get stuck in an endless repetition. For example, forgetting to update the loop condition or break statement.

Reason: A poorly implemented JavaScript function causes a webpage to freeze or become unresponsive.

6). Memory Leak: Occurs when a program fails to release memory that is no longer in use, leading to memory consumption issues over time.

Reason: A web application continuously loads data without properly releasing memory resources, leading to slower performance or crashes over time.

7). Race Condition: A situation where the behavior of a program depends on the timing or sequence of events. For example, multiple threads accessing and modifying the same shared resource concurrently.

Reason: Multiple users simultaneously update the same data on a collaborative platform, resulting in data inconsistencies or incorrect merging of changes.

8). Buffer Overflow: Happens when a program tries to store more data in a buffer than it can hold, potentially leading to overwriting adjacent memory locations.

Reason: A poorly secured input field on a website allows a user to enter a long string of characters, causing a buffer overflow vulnerability that can be exploited.

9). Division by Zero: A mathematical error that occurs when attempting to divide a number by zero.

Reason: A mathematical calculation on a website fails to handle the possibility of dividing by zero, leading to an error or unexpected behaviour.

10). Deadlock: Occurs when two or more processes are unable to proceed because each is waiting for the other to release a resource.

Reason: Multiple users attempt to access a limited resource, such as a shared document, simultaneously, resulting in a deadlock where none of them can proceed.

11). _Out of Bounds Error: _Happens when a program tries to access an element outside the boundaries of an array or container.

Reason: A user navigates to a non-existent page on a website and encounters a 404 error page.

12). Unhandled Exception: An exception that is not properly caught or handled by the program, leading to unexpected behavior or crashes.

Reason: An error occurs during the processing of a user's request on a website, but instead of gracefully handling the error, a generic error message is displayed.

13). File Not Found Error: When a program attempts to access a file that doesn't exist in the specified location.

Reason: A user clicks on a broken link or enters an incorrect URL, resulting in a "404 Not Found" error page.

14). Type Conversion Error: Happens when incompatible data types are used incorrectly or not properly converted.

Reason: A form on a website fails to convert a user's input to the correct data type, leading to incorrect calculations or data processing.