{"id":301,"date":"2013-11-07T09:31:00","date_gmt":"2013-11-07T09:31:00","guid":{"rendered":"https:\/\/kiencang.net\/2013\/11\/07\/bo-chon-hay-selector-trong-css\/"},"modified":"2013-11-07T09:31:00","modified_gmt":"2013-11-07T09:31:00","slug":"bo-chon-hay-selector-trong-css","status":"publish","type":"post","link":"https:\/\/kiencang.net\/bo-chon-hay-selector-trong-css\/","title":{"rendered":"Selector trong CSS l\u00e0 g\u00ec? B\u1ea1n c\u00f3 th\u1ec3 kh\u00f4ng bi\u1ebft r\u1ea5t nhi\u1ec1u selector th\u00fa v\u1ecb \u0111\u1ea5y!"},"content":{"rendered":"\n<p>Trong khi thao t\u00e1c CSS, <strong>b\u1ed9 ch\u1ecdn (selector)<\/strong> l\u00e0 c\u00e1i \u0111\u01b0\u1ee3c vi\u1ebft ra \u0111\u1ea7u ti\u00ean. N\u00f3 l\u00e0 \u0111\u1ed1i t\u01b0\u1ee3ng m\u00e0 ch\u00fang ta mu\u1ed1n t\u00e1c \u0111\u1ed9ng, ti\u1ebfp theo m\u1edbi vi\u1ebft c\u00e1c <strong>khai b\u00e1o<\/strong>, trong khai b\u00e1o c\u00f3 <strong>thu\u1ed9c t\u00ednh<\/strong> v\u00e0 <strong>gi\u00e1 tr\u1ecb<\/strong> (xem th\u00eam <a href=\"https:\/\/kiencang.net\/cu-phap-cua-css\/\" target=\"_blank\" rel=\"noreferrer noopener\">c\u00fa ph\u00e1p c\u1ee7a CSS<\/a>).<\/p>\n\n\n\n<p>\u0110\u1ec5 cho d\u1ec5 t\u01b0\u1edfng t\u01b0\u1ee3ng h\u01a1n, gi\u1ea3 d\u1ee5 b\u1ea1n l\u00e0 th\u1ee3 s\u01a1n chuy\u00ean nghi\u1ec7p, kh\u00e1ch h\u00e0ng alo cho b\u1ea1n, anh ta mu\u1ed1n s\u01a1n ng\u00f4i nh\u00e0 c\u00f3 m\u00e0u xanh, v\u00e0 c\u00e1c vi\u1ec1n c\u1eeda m\u00e0u n\u00e2u. <\/p>\n\n\n\n<p>OK, chuy\u1ec7n \u0111\u00f3 ch\u1eb3ng kh\u00f3 g\u00ec v\u1edbi b\u1ea1n, th\u1ebf nh\u01b0ng n\u1ebfu kh\u00e1ch h\u00e0ng kh\u00f4ng cho bi\u1ebft \u0111\u1ecba ch\u1ec9 c\u1ee5 th\u1ec3 c\u1ee7a ng\u00f4i nh\u00e0 th\u00ec b\u1ea1n bi\u1ebft s\u01a1n v\u00e0o \u0111\u00e2u? \u0110\u1ecba ch\u1ec9 ng\u00f4i nh\u00e0 c\u00f3 th\u1ec3 n\u00f3i l\u00e0 selector. D\u01b0\u1edbi \u0111\u00e2y l\u00e0 c\u00e1c d\u00f2ng code th\u1ef1c t\u1ebf. Th\u00ed d\u1ee5:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>#menu {\nfont-size: 18px;\nbackground-color: lime;\n}<\/code><\/pre>\n\n\n\n<p>C\u00e1i&nbsp;<strong>#menu<\/strong>&nbsp;ch\u00ednh l\u00e0&nbsp;<strong>b\u1ed9 ch\u1ecdn<\/strong>.<\/p>\n\n\n\n<p>N\u1ebfu kh\u00f4ng n\u1eafm r\u00f5 v\u1ec1 selector, b\u1ea1n s\u1ebd g\u1eb7p kh\u00f3 kh\u0103n trong vi\u1ec7c CSS, r\u1ea5t c\u00f3 th\u1ec3 b\u1ea1n s\u1ebd l\u1ea1m d\u1ee5ng <a href=\"https:\/\/kiencang.net\/id-class-css\/\" target=\"_blank\" rel=\"noreferrer noopener\">id v\u00e0 class<\/a>, c\u00e1c \u0111o\u1ea1n m\u00e3 b\u1ecb r\u1ed1i lo\u1ea1n, ch\u1ed3ng ch\u00e9o v\u00e0 thi\u1ebfu ki\u1ec3m so\u00e1t.<\/p>\n\n\n\n<hr class=\"wp-block-separator\"\/>\n\n\n\n<p>C\u00e2u h\u1ecfi \u0111\u1ea7u ti\u00ean, CSS c\u00f3 nh\u1eefng b\u1ed9 ch\u1ecdn n\u00e0o?<\/p>\n\n\n\n<ul><li>Selector t\u1ea5t c\u1ea3 c\u00e1c th\u00e0nh ph\u1ea7n HTML (v\u00ed d\u1ee5 <code>p{}<\/code>, <code>div{}<\/code>, <code>span{}<\/code>);<\/li><li>Selector c\u00e1c th\u00e0nh ph\u1ea7n c\u00f3 c\u00f9ng t\u00ean class (v\u00ed d\u1ee5 <code>.freehostpage{}<\/code>);<\/li><li>Selector c\u00e1c th\u00e0nh ph\u1ea7n c\u00f3 c\u00f9ng t\u00ean id (v\u00ed d\u1ee5 <code>#freehostpage{}<\/code>);<\/li><li>Selector c\u00e1c th\u1ebb c\u00f9ng lo\u1ea1i (v\u00ed d\u1ee5 <code>p{}<\/code>);<\/li><li>Selector nhi\u1ec1u th\u1ebb kh\u00e1c nhau (v\u00ed d\u1ee5 <code>p, u, i{}<\/code>);<\/li><li>Selector th\u00e0nh ph\u1ea7n n\u1eb1m trong th\u00e0nh ph\u1ea7n kh\u00e1c (v\u00ed d\u1ee5 <code>p ul li {}<\/code>);<\/li><li>Selector th\u00e0nh ph\u1ea7n ph\u1ea3i l\u00e0 con c\u1ee7a th\u00e0nh ph\u1ea7n kh\u00e1c (v\u00ed d\u1ee5 <code>p > ul li {}<\/code>);<\/li><li>Selector c\u00e1c l\u1edbp gi\u1ea3 (v\u00ed d\u1ee5 <a href=\"https:\/\/kiencang.net\/lop-gia-first-child-trong-css\/\" target=\"_blank\" rel=\"noreferrer noopener\">first child<\/a>);<\/li><li>Selector d\u1ef1a v\u00e0o <a href=\"https:\/\/kiencang.net\/selector-thuoc-tinh-trong-css\/\" target=\"_blank\" rel=\"noreferrer noopener\">thu\u1ed9c t\u00ednh c\u1ee7a th\u1ebb<\/a>;<\/li><\/ul>\n\n\n\n<hr class=\"wp-block-separator\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">1. Ch\u1ecdn t\u1ea5t c\u1ea3 c\u00e1c th\u00e0nh ph\u1ea7n HTML<\/h3>\n\n\n\n<p>S\u1eed d\u1ee5ng d\u1ea5u * \u0111\u1ec3 ch\u1ecdn t\u1ea5t c\u1ea3 c\u00e1c th\u00e0nh ph\u1ea7n c\u1ee7a HTML, v\u00ed d\u1ee5:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>* {\n    margin: 0;\n    padding: 0;\n}<\/code><\/pre>\n\n\n\n<p>B\u1ea1n c\u00f3 th\u1ea5y \u0111o\u1ea1n code tr\u00ean quen quen kh\u00f4ng? n\u00f3 th\u01b0\u1eddng d\u00f9ng \u0111\u1ec3&nbsp;<a href=\"https:\/\/kiencang.net\/khu-cac-thiet-lap-mac-dinh-cua-trinh-duyet-trong-css\/\" target=\"_blank\" rel=\"noreferrer noopener\">kh\u1eed m\u1eb7c \u0111\u1ecbnh tr\u00ecnh duy\u1ec7t v\u1ec1 l\u1ec1 v\u00e0 \u0111\u1ec7m<\/a>&nbsp;c\u1ee7a&nbsp;t\u1ea5t c\u1ea3&nbsp;c\u00e1c th\u1ebb trong HTML.<\/p>\n\n\n\n<hr class=\"wp-block-separator\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">2. Ch\u1ecdn t\u1ea5t c\u1ea3 th\u00e0nh ph\u1ea7n c\u00f3 c\u00f9ng t\u00ean class<\/h3>\n\n\n\n<p>S\u1eed d\u1ee5ng d\u1ea5u ch\u1ea5m (.) theo sau \u0111\u00f3 l\u00e0 t\u00ean class \u0111\u1ec3 l\u00e0m b\u1ed9 ch\u1ecdn, th\u00ed d\u1ee5 ta c\u00f3 m\u00e3 \u0111\u00e1nh d\u1ea5u HTML nh\u01b0 sau:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>&lt;h2 class=\"tieude\"&gt;Ki\u1ebfn c\u00e0ng&lt;\/h2&gt;<\/code><\/pre>\n\n\n\n<p>\u0110\u1ec3 t\u00e1c \u0111\u1ed9ng v\u00e0o c\u00e1c th\u1ebb c\u00f3 class l\u00e0 tieude, trong CSS vi\u1ebft:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>.tieude {\n   color: red;\n}<\/code><\/pre>\n\n\n\n<p>L\u01b0u \u00fd: t\u1ea5t c\u1ea3 c\u00e1c class c\u00f3 c\u00f9ng t\u00ean \u0111\u1ec1u b\u1ecb t\u00e1c \u0111\u1ed9ng b\u1edfi c\u00e2u l\u1ec7nh tr\u00ean.<\/p>\n\n\n\n<hr class=\"wp-block-separator\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">3. Ch\u1ecdn th\u00e0nh ph\u1ea7n c\u00f3 t\u00ean id<\/h3>\n\n\n\n<p>V\u1edbi id, s\u1eed d\u1ee5ng d\u1ea5u # \u0111\u1ec3 b\u1eaft \u0111\u1ea7u b\u1ed9 ch\u1ecdn, sau \u0111\u1ea5y l\u00e0 t\u00ean c\u1ee7a \u00edd, v\u00ed d\u1ee5 \u0111\u1ea7u b\u00e0i v\u1ec1 menu ch\u00ednh l\u00e0 minh h\u1ecda v\u1ec1 c\u00e1ch s\u1eed d\u1ee5ng id l\u00e0m selector.<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>#menu {\nfont-size: 18px;\n}<\/code><\/pre>\n\n\n\n<p>B\u1ea1n c\u00f3 th\u1ec3 \u0111\u1ecdc b\u00e0i vi\u1ebft s\u1ef1&nbsp;<a href=\"https:\/\/kiencang.net\/id-class-css\/\" target=\"_blank\" rel=\"noreferrer noopener\">gi\u1ed1ng v\u00e0 kh\u00e1c nhau gi\u1eefa id v\u00e0 class<\/a>&nbsp;\u0111\u1ec3 c\u00f3 th\u00eam th\u00f4ng tin.<\/p>\n\n\n\n<hr class=\"wp-block-separator\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">4. Ch\u1ecdn t\u1ea5t c\u1ea3 c\u00e1c th\u1ebb c\u00f9ng lo\u1ea1i<\/h3>\n\n\n\n<p>Th\u00ed d\u1ee5 t\u00f4i mu\u1ed1n v\u0103n b\u1ea3n c\u00f3 font l\u00e0 arial th\u00ec vi\u1ebft nh\u01b0 n\u00e0y:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>p {\n   font-family: Arial Helvetica sans-serif;\n}<\/code><\/pre>\n\n\n\n<p>Khi \u1ea5y, b\u1ea5t k\u1ef3 v\u0103n b\u1ea3n n\u00e0o trong trang web \u0111\u1ec1u \u0111\u01b0\u1ee3c&nbsp;<a href=\"https:\/\/kiencang.net\/5-thuoc-tinh-cua-font-trong-css\/\" target=\"_blank\" rel=\"noreferrer noopener\">quy \u0111\u1ecbnh font<\/a>&nbsp;l\u00e0 Arial\u2026T\u01b0\u01a1ng t\u1ef1, c\u00e2u l\u1ec7nh:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>h2 {\n   margin-left: 10px;\n   padding: 5px;\n}<\/code><\/pre>\n\n\n\n<hr class=\"wp-block-separator\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">5. Ch\u1ecdn nhi\u1ec1u th\u1ebb kh\u00e1c nhau c\u00f9ng m\u1ed9t l\u00fac<\/h3>\n\n\n\n<p>Gi\u1ea3 d\u1ee5 n\u1ebfu b\u1ea1n mu\u1ed1n c\u1ea3 th\u1ebb h2, h3 v\u00e0 th\u1ebb p c\u00f9ng c\u00f3 l\u1ec1 tr\u00ean l\u00e0 10px th\u00ec vi\u1ebft nh\u01b0 sau:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>h2, h3, p {\n   margin-top: 10px;\n}<\/code><\/pre>\n\n\n\n<p>L\u01b0u \u00fd:<\/p>\n\n\n\n<ul><li>C\u00e1c th\u1ebb ng\u0103n nhau b\u1eb1ng d\u1ea5u ph\u1ea9y;<\/li><li>Kh\u00f4ng gi\u1edbi h\u1ea1n s\u1ed1 th\u1ebb;<\/li><\/ul>\n\n\n\n<p>T\u00e1c d\u1ee5ng l\u1edbn nh\u1ea5t c\u1ee7a selector n\u00e0y l\u00e0 n\u00f3 gi\u00fap ch\u00fang ta \u0111\u1ee1 ph\u1ea3i vi\u1ebft code l\u1eb7p \u0111i l\u1eb7p l\u1ea1i.<\/p>\n\n\n\n<hr class=\"wp-block-separator\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">6. Ch\u1ecdn th\u00e0nh ph\u1ea7n n\u1eb1m trong m\u1ed9t th\u00e0nh ph\u1ea7n kh\u00e1c<\/h3>\n\n\n\n<p>C\u00e2u l\u1ec7nh:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>div h3 {\n    font-weight: normal;\n}<\/code><\/pre>\n\n\n\n<p>D\u00f2ng code tr\u00ean s\u1ebd l\u00e0m t\u1ea5t c\u1ea3 c\u00e1c th\u1ebb h3 n\u1eb1m trong div \u0111\u1ec1u ch\u1ecbu \u1ea3nh h\u01b0\u1edfng c\u1ee7a l\u1ec7nh, d\u00f9 l\u00e0 th\u1ebb con, ch\u00e1u, ch\u1eaft\u2026c\u1ee7a div.<\/p>\n\n\n\n<hr class=\"wp-block-separator\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">7. Ch\u1ecdn ch\u00ednh x\u00e1c th\u00e0nh ph\u1ea7n ph\u1ea3i l\u00e0 con c\u1ee7a m\u1ed9t th\u00e0nh ph\u1ea7n kh\u00e1c<\/h3>\n\n\n\n<p>C\u00e2u l\u1ec7nh:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>#right&gt;h2{\n   font-size: 12px;\n   color: blue;\n}<\/code><\/pre>\n\n\n\n<p>Selector tr\u00ean s\u1ebd ch\u1ecdn t\u1ea5t c\u1ea3 c\u00e1c th\u1ebb h2 l\u00e0 con c\u1ee7a id c\u00f3 t\u00ean l\u00e0 right. C\u00f3 b\u1ea1n s\u1ebd h\u1ecfi: c\u00e2u l\u1ec7nh n\u00e0y v\u1edbi c\u00e2u l\u1ec7nh&nbsp;<em>ch\u1ecdn th\u00e0nh ph\u1ea7n n\u1eb1m trong m\u1ed9t th\u00e0nh ph\u1ea7n kh\u00e1c<\/em>&nbsp;c\u00f3 g\u00ec kh\u00e1c nhau?<\/p>\n\n\n\n<p>S\u1ef1 kh\u00e1c nhau n\u1eb1m \u1edf \u0111\u1ed9 s\u00e2u c\u1ee7a t\u00e1c \u0111\u1ed9ng. M\u1ed9t c\u00e1i t\u00e1c \u0111\u1ed9ng r\u1ea5t s\u00e2u v\u00e0 r\u1ed9ng v\u00e0o m\u1ecdi th\u00e0nh ph\u1ea7n con v\u00e0 ch\u00e1u, c\u00f2n m\u1ed9t c\u00e1i ch\u1ec9 t\u00e1c \u0111\u1ed9ng v\u00e0o c\u00e1c th\u1ebb n\u00e0o l\u00e0 con m\u00e0 th\u00f4i.<\/p>\n\n\n\n<hr class=\"wp-block-separator\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">8. Ch\u1ecdn c\u00e1c l\u1edbp gi\u1ea3<\/h3>\n\n\n\n<p>C\u00e1c l\u1edbp gi\u1ea3 bao g\u1ed3m :link, :hover, :visited, :active, :focus,&nbsp;<a href=\"https:\/\/kiencang.net\/lop-gia-first-letter-trong-css\/\">:first-letter<\/a>, :first-line,&nbsp;<a href=\"https:\/\/kiencang.net\/lop-gia-first-child-trong-css\/\">:first-child<\/a>,&nbsp;<a href=\"https:\/\/kiencang.net\/selector-before-trong-css\/\">:before<\/a>,&nbsp;<a href=\"https:\/\/kiencang.net\/selector-after-trong-css\/\">:after<\/a>, :lang (m\u00e3 ng\u00f4n ng\u1eef) \u2013 n\u1ed5i ti\u1ebfng nh\u1ea5t trong nh\u00f3m n\u00e0y l\u00e0 hover. V\u00ed d\u1ee5:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>a:hover {\n   color: gray;\n}<\/code><\/pre>\n\n\n\n<p>C\u00e2u l\u1ec7nh n\u00e0y l\u00e0m cho ng\u01b0\u1eddi d\u00f9ng khi di chu\u1ed9t qua li\u00ean k\u1ebft th\u00ec link \u0111\u1ed5i sang m\u00e0u x\u00e1m. \u0110\u1ecdc th\u00eam b\u00e0i&nbsp;<a href=\"https:\/\/kiencang.net\/chinh-sua-css-cho-the-a\/\">CSS cho th\u1ebb a<\/a>&nbsp;\u0111\u1ec3 bi\u1ebft chi ti\u1ebft h\u01a1n c\u00e1ch t\u1ea1o style cho li\u00ean k\u1ebft.<\/p>\n\n\n\n<hr class=\"wp-block-separator\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">9. Ch\u1ecdn d\u1ef1a v\u00e0o thu\u1ed9c t\u00ednh c\u1ee7a th\u1ebb<\/h3>\n\n\n\n<p>B\u1ea1n ch\u1ecdn th\u1ebb mu\u1ed1n t\u00e1c \u0111\u1ed9ng d\u1ef1a v\u00e0o thu\u1ed9c t\u00ednh c\u1ee7a n\u00f3, th\u00ed d\u1ee5 \u0111o\u1ea1n code sau:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>&lt;!DOCTYPE html&gt;\n&lt;html&gt;\n&lt;head&gt;\n&lt;style&gt;\na&#91;target=_blank]\n{\nbackground-color:lime;\n}\n&lt;\/style&gt;\n&lt;\/head&gt;\n&lt;body&gt;\n \n&lt;a href=\"http:\/\/vi.wikipedia.org\"&gt;vi.wikipedia.org&lt;\/a&gt;\n&lt;a href=\"freehost.page\" <strong>target=\"_blank\"<\/strong>&gt;Ki\u1ebfn c\u00e0ng&lt;\/a&gt;\n&lt;a href=\"http:\/\/vnexpress.net\"&gt;vnexpress.net&lt;\/a&gt;\n \n&lt;\/body&gt;\n&lt;\/html&gt;<\/code><\/pre>\n\n\n\n<p>C\u00f3 3 th\u1ebb a trong body, nh\u01b0ng b\u1eb1ng c\u00e1ch s\u1eed d\u1ee5ng thu\u1ed9c t\u00ednh \u0111\u1ec3 t\u00e1c \u0111\u1ed9ng, l\u00e0m cho ch\u1ec9 th\u1ebb a \u1edf gi\u1eefa c\u00f3 m\u00e0u n\u1ec1n l\u00e0 lime, 2 th\u1ebb a c\u00f2n l\u1ea1i kh\u00f4ng b\u1ecb \u1ea3nh h\u01b0\u1edfng g\u00ec.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Trong khi thao t\u00e1c CSS, b\u1ed9 ch\u1ecdn (selector) l\u00e0 c\u00e1i \u0111\u01b0\u1ee3c vi\u1ebft ra \u0111\u1ea7u ti\u00ean. N\u00f3 l\u00e0 \u0111\u1ed1i t\u01b0\u1ee3ng m\u00e0 ch\u00fang ta mu\u1ed1n t\u00e1c \u0111\u1ed9ng, ti\u1ebfp theo m\u1edbi vi\u1ebft c\u00e1c khai b\u00e1o, trong khai b\u00e1o c\u00f3 thu\u1ed9c t\u00ednh v\u00e0 gi\u00e1 tr\u1ecb (xem th\u00eam c\u00fa ph\u00e1p c\u1ee7a CSS). \u0110\u1ec5 cho d\u1ec5 t\u01b0\u1edfng t\u01b0\u1ee3ng h\u01a1n, gi\u1ea3 d\u1ee5 &hellip;<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[229],"tags":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v21.6 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>Selector trong CSS l\u00e0 g\u00ec? B\u1ea1n c\u00f3 th\u1ec3 kh\u00f4ng bi\u1ebft r\u1ea5t nhi\u1ec1u selector th\u00fa v\u1ecb \u0111\u1ea5y! &#8226; Ki\u1ebfn c\u00e0ng<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/kiencang.net\/bo-chon-hay-selector-trong-css\/\" \/>\n<meta property=\"og:locale\" content=\"vi_VN\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Selector trong CSS l\u00e0 g\u00ec? B\u1ea1n c\u00f3 th\u1ec3 kh\u00f4ng bi\u1ebft r\u1ea5t nhi\u1ec1u selector th\u00fa v\u1ecb \u0111\u1ea5y! &#8226; Ki\u1ebfn c\u00e0ng\" \/>\n<meta property=\"og:description\" content=\"Trong khi thao t\u00e1c CSS, b\u1ed9 ch\u1ecdn (selector) l\u00e0 c\u00e1i \u0111\u01b0\u1ee3c vi\u1ebft ra \u0111\u1ea7u ti\u00ean. 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