docs(10_Wiki): W3Schools 위키화 — HTML/CSS/JavaScript(core)

W3Schools 튜토리얼을 P-Reinforce v3.1 포맷으로 위키화(영어 본문, 한/영 섹션 헤더).
- Topic_HTML: 59문서 (튜토리얼+예제, 레퍼런스/메타 제외)
- Topic_CSS: 190문서 (메인 + Advanced/Flexbox/Grid/RWD 전체)
- Topic_JavaScript: 120문서 (코어 언어; Temporal/DOM상세/BOM/WebAPI/AJAX/jQuery/Graphics 등은 후속)
각 폴더 00_INDEX.md(MOC) 포함. 코드 verbatim, 미확인분은 "Not found in source" 표기.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

10_Wiki/Topic_CSS/CSS_Background_Attachment.md

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+---
+id: css-background-attachment
+title: "CSS Background Attachment"
+category: "Frontend"
+status: "draft"
+verification_status: "conceptual"
+canonical_id: ""
+aliases: ["background-attachment", "fixed background", "scroll background", "CSS background attachment", "fixed vs scroll"]
+duplicate_of: ""
+source_trust_level: "B"
+confidence_score: 0.88
+created_at: 2026-06-23
+updated_at: 2026-06-23
+review_reason: ""
+merge_history: []
+tags: ["css", "web", "frontend", "w3schools", "background", "background-attachment"]
+raw_sources: ["https://www.w3schools.com/css/css_background_attachment.asp"]
+applied_in: []
+github_commit: ""
+---
+
+# [[CSS Background Attachment]]
+
+## 🎯 한 줄 통찰 (One-line insight)
+The `background-attachment` property specifies whether a background image is `fixed` (does not scroll with the rest of the page) or `scroll` (scrolls along with the page). [S1]
+
+## 🧠 핵심 개념 (Core concepts)
+- **background-attachment** — specifies whether the background image should scroll or be fixed. [S1]
+- **fixed** — the background image will not scroll with the rest of the page; it stays in place relative to the viewport. [S1]
+- **scroll** — the background image scrolls with the rest of the page. [S1]
+- **Combines with other background properties** — typically set alongside `background-image`, `background-repeat`, and `background-position`. [S1]
+
+## 🧩 추출된 패턴 (Extracted patterns)
+- **Anchored backdrop** — use `fixed` to keep an image stationary while content scrolls over it. [S1]
+- **Flowing backdrop** — use `scroll` so the image moves together with the page content. [S1]
+
+## 📖 세부 내용 (Details)
+**background-attachment: fixed**
+Specify that the background image should be fixed (will not scroll with the rest of the page): [S1]
+```css
+body {
+  background-image: url("img_tree.png");
+  background-repeat: no-repeat;
+  background-position: right top;
+  background-attachment: fixed;
+}
+```
+
+**background-attachment: scroll**
+Specify that the background image should scroll with the rest of the page: [S1]
+```css
+body {
+  background-image: url("img_tree.png");
+  background-repeat: no-repeat;
+  background-position: right top;
+  background-attachment: scroll;
+}
+```
+
+**Property reference (from the page table):** [S1]
+
+| Property | Description |
+|----------|-------------|
+| `background-attachment` | Sets whether a background image is fixed or scrolls with the rest of the page |
+
+## 🛠️ 적용 사례 (Applied in summary)
+The CSS rules above are the page's own demonstration examples on `body`. No external project/commit applications found in the source.
+
+## 💻 코드 패턴 (Code patterns)
+Fixed (stationary) background (language: CSS):
+```css
+body {
+  background-image: url("img_tree.png");
+  background-repeat: no-repeat;
+  background-position: right top;
+  background-attachment: fixed;
+}
+```
+Scrolling background:
+```css
+body {
+  background-image: url("img_tree.png");
+  background-repeat: no-repeat;
+  background-position: right top;
+  background-attachment: scroll;
+}
+```
+
+## ⚖️ 비교 및 선택 기준 (Comparison & decision criteria)
+- **fixed vs scroll** — `fixed` keeps the background image stationary (does not scroll with the rest of the page), while `scroll` makes the image scroll together with the page content. [S1]
+
+## ⚖️ 모순 및 업데이트 (Contradictions & updates)
+No contradictions found in the source.
+
+## ✅ 검증 상태 및 신뢰도
+- **상태:** draft
+- **검증 단계:** conceptual (실제 적용 사례 발견 시 applied/validated로 승격 가능)
+- **출처 신뢰도:** B (W3Schools — widely used educational reference, not a primary standards body)
+- **신뢰 점수:** 0.88
+- **중복 검사 결과:** 신규 생성 (New discovery)
+
+## 🔗 지식 그래프 (Knowledge Graph)
+- **상위/루트:** [[CSS Tutorial]]
+- **관련 개념:** [[CSS Background Image]], [[CSS Background Repeat]], [[CSS Background Shorthand]], [[CSS Background Color]]
+- **참조 맥락:** Referenced when deciding whether a background image stays put or moves as the user scrolls.
+
+## 📚 출처 (Sources)
+- [S1] W3Schools — CSS Background Attachment — https://www.w3schools.com/css/css_background_attachment.asp
+
+## 📝 변경 이력 (Change history)
+- 2026-06-23: Initial draft synthesized from the W3Schools "CSS Background Attachment" page (Astra wiki-curation, P-Reinforce v3.1 format).