Visualforce page that checks the size of a file selected for upload

CheckAttachmentSize.page

<apex:page standardController="Account" extensions="AddAttachmentExt">
  <apex:includeScript value="https://ajax.aspnetcdn.com/ajax/jQuery/jquery-1.9.1.min.js"/>
  <apex:form>
    <apex:sectionHeader title="{!Account.name} Attachments" />
    <apex:pageBlock mode="maindetail">
      <apex:pageBlockSection title="Existing Attachments" columns="1">
        <apex:PageBlockTable value="{!Account.Attachments}" var="attach">
          <apex:column value="{!attach.Name}" />
          <apex:column headerValue="Length (bytes)" value="{!attach.BodyLength}" />
          <apex:column headerValue="Owner" value="{!attach.Owner.Name}" />
        </apex:PageBlockTable>
      </apex:pageBlockSection>
      <apex:pageBlockSection title="Add Attachment">
        <apex:inputFile filename="{!att.Name}"  value="{!att.Body}" />
        <apex:commandButton value="Upload" action="{!addAttachment}" onclick="return checkFileSize();"/>
      </apex:pageBlockSection>
    </apex:pageBlock>
  </apex:form>
  
  <script>
    function getIEFileSize(file){
        var myFSO = new ActiveXObject("Scripting.FileSystemObject"),
        filepath = file.value,
        thefile = myFSO.getFile(filepath);
        return thefile.size;
    }

    function checkFileSize()
    {
        var goodSize = true;
        $('input[type=file]').each(function()
        {
            if(typeof this.files[0] !== 'undefined')
            {
                var file = this.files[0],
                size = typeof ActiveXObject !== 'undefined' ?
                    getIEFileSize(file)
                    :
                    file.fileSize || file.size;

                goodSize = 25000000 > size;
                if(!goodSize)
                {
                    alert(this.files[0].name +' is too large - please choose a file that is 25Mb or less');
                }
                else
                {
                	if (2000000 < size)
                	{
                    	goodSize=confirm('The file size is ' + size + 
                    		' bytes - this may take some time. Are you sure you wish to continue');
                    }
                }

                return goodSize;
            }
        });
        return goodSize;
    }

  </script>
</apex:page>