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<html><head><style> #myDIV { width: 300px; height: 300px; margin-top: 20px; background-color: lightgreen; border-block-start: 10px solid black;}</style></head><body><h1>Change border-block-start with JavaScript</h1><p>Click the "Try it" button to change the border-block-start property of the DIV element:</p><button onclick="myFunction()">Try it</button><div id="myDIV"> <h1>Hello</h1></div><script>function myFunction() { document.getElementById("myDIV").style.borderBlockStart = "15px dotted pink";}</script></body></html>