Q:

html can't click on checkboxes

This is my html:
<div style="width: 45%; float: left; margin-left:5%">
                    <div class="chartHeaderClass" style="width: 100%;">
                        <h3>Service Level Per Campaign</h3>
                        <%-- Start Dropdown Code --%>
                        <a id="DropdownSeviceLink" href="#">+</a>
                        <div ID="campaignDiv" runat="server" ><ul>

                                              </ul>
                        </div>
                        <script type="text/javascript" src="Scripts/DropdownCheckbox.js"></script>
                        <%-- End Dropdown Code --%>
                    </div>
                    <div id="line-chart" class="chart-holder" style="border:1px solid #D5D5D5; margin-top:2px">
                        <canvas class="overlay" width="479" height="265"></canvas>
                    </div>
                </div>
                <div style="width: 45%; float: right">
                    <div class="chartHeaderClass" style="width: 100%;">
                        <h3>Calls Per Campaign</h3>
                    </div>
                    <div id="pie-chart" class="chart-holder" style="border:1px solid #D5D5D5; margin-top:2px">
                        <canvas class="overlay" width="479" height="265"></canvas>
                    </div>
                </div>

notice that it has this div campaignDiv which I fill in c# like this:
if (!IsPostBack) {
                List<string> comps = getCompainNames();
                string html = "<ul>";
                for (int i = 0; i < comps.Count(); i++) {
                    html = html + CreateLiCheckbox(comps[i]);
                }
                html = html + "</ul>";
                campaignDiv.InnerHtml = html;
            }
private string CreateLiCheckbox(string checkBoxText)
        {
            return string.Format("<li><input type=\"checkbox\">{0}</li>", checkBoxText);
        }

This result is this:

I can't click on the checkboxes. In other words, when I click on them nothing happens
I noticed something
I can't select the text inside the red area. It seems that it is not exit because when I tried to select it using the mouse, nothing becomes selected.
could u help please?
css for this red area is 
#DropdownSeviceLink {
    float:right;
    margin-right:10px;
}
a#DropdownServiceLink:visited {
    color:inherit;
}
#campaignDiv {
    background-color:red;
    width:200px;
    height:200px;
    float:right;
    position:relative;
}

Finally the context of my page is
when clicking on that plus sign, I want to show this red area, I can do that on jquery, but I just told you the context maybe that helps
jsfiddle
http://jsfiddle.net/jdhMs/

A:

I had this exact same issue in my application and it turned out that the div I had my checkboxes in was being overlapped by the footer of the modal box. Since the footer of the modal box was white/transparent, this wasn't evident until I added a border around the footer. Only then I was able to see that I could see the checkboxes but couldn't actually select them.

