Can multiple different HTML elements have the same ID if they're different elements?

Uniqueness is golden: why ID repetition is harmful

Dual-use of IDs is a big no-no. It can inadvertently cause JavaScript errors and obstruct accessibility, creating UX nightmares.

Code ambiguity: the downside of duplicate IDs

When it comes to JavaScript, getElementById only sees the first twin id and turns a blind eye to the rest, potentially derailing DOM manipulation:

document.getElementById("twinId"); // Sees only the first 'twinId', other is left sulking
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On the CSS front, styling might become a guessing game. While browsers may apply styles to all same IDs, this behavior is fickle, violating CSS predictability:

#twinId { 
  color: red; 
} 
/* All twinId elements may blush red, or maybe not */
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Duty of care for comprehensive code and future-proofing

Avoid the heartbreak of broken code. Upholding web standards by using unique IDs ensures your code won't crack tomorrow. Plus, your future self will thank you for your tidy, maintainable code.

When many is merrier: CSS classes

For uniform styles or behavior across multiple elements, don't clone IDs. Let classes save the day:

<div class="mirrorStyle"></div>
<button class="mirrorStyle"></button>
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Harness the power of IDs and classes together—IDs for individuality, classes for community.

Miles to go: Beyond just clean code

Distinct IDs also ensure web accessibility. Assistive devices lean on unique identifiers for seamless navigation.

Maintaining document’s sanctity

Dual IDs might also botch up form labeling and intra-page links, thereby spoiling the user experience:

• Form labels join hands with inputs using the for attribute, which expects a one and only one!
• In-page anchors rely on unique IDs to jump to various sections of the page.

Weather-proofing your work

As web standards march on and browsers evolve, sticking to the unique ID mandate ensures your website stays compatible and future-proof.

Note to self: Web dev best practices

• Validate your HTML zealously using tools like W3C's validator to catch any duplicate IDs.
• Schedule regular code reviews to ensure ID uniqueness and consistent use of class names.