Question: I have to support IE8. The modal itself works fine, but my attempts to resize it (which work fine in Firefox) don't work in IE8.

I'm just adding a class (wide-modal in this example) to the modal-dialog div (the 2nd nested one in the Bootstrap structure) and applying a width via CSS, nothing fancy.

HTML:

```
       <div class="modal fade" id="modalTest" role="dialog">
            <div class="modal-dialog wide-modal">
              <div class="modal-content ">
                <div class="modal-header">
                  <button type="button" class="close" data-dismiss="modal" aria-hidden="true">&times;</button>
                  <h4 class="modal-title">Testing Modal</h4>
                </div>
                <div class="modal-body">
                  <img src="content/Example-Infographic.jpg" width="100%" />
                </div>
                <div class="modal-footer">
                  <button type="button" class="btn btn-default" data-dismiss="modal">Close</button>
                </div>
              </div><!-- /.modal-content -->
            </div><!-- /.modal-dialog -->
        </div>

```

CSS:

```
.wide-modal {
    width: 60%;
}

```

I tried adding the class to the div above and below to no (positive) effect. It works like a charm where it is in Firefox, just no effect at all in IE8. I also tried with a px width, no difference. I do have the respond.js library in place so in general IE8 is behaving other than this.

Answer: 
In bootstrap 3 you need assign width not to `.modal` class but to `.modal-dialog`

```
#modalTest .modal-dialog
{
    width: 500px; /* your width */
}

```
I think you need to set the width in pixels and adjust the margin-left. For example,

```
.modal-dialog {
    width:700px;
    margin-left:-320px;
}

```

The margin left must be half the width of the modal, minus 30px for the scrollbar.

Here's an example on Bootply: <http://bootply.com/85213>