- <div id="div1" style="width:500px; height:300px;"></div>
- <div id="div2" style="width:500px; height:300px;"></div>
- <div id="div3" style="width:500px; height:300px;"></div>
- <div id="div4" style="width:500px; height:300px;"></div>
+ <div class="chart-container">
+ <div id="div1" class="chart"></div>
+ <div id="div2" class="chart"></div>
+ <div id="div3" class="chart"></div>
+ <div id="div4" class="chart"></div>
+ </div>
+
+ <p>
+ Synchronize what?
+ <input type=checkbox id='chk-zoom' checked onChange='update()'><label for='chk-zoom'> Zoom</label>
+ <input type=checkbox id='chk-selection' checked onChange='update()'><label for='chk-selection'> Selection</label>
+ </p>