Many people are posting the woes of DotNet Postbacks not working in IE11. I too experienced this and remembered that there were app_browser files that could be modified to give the browser further instructions. With a quick google search I was able to find the exact solution that I was looking for. I cannot take credit for it so I will share the original URL from which I got my answer. [ Answer ]
However Here is the code so you do not have to click on the link above:
<browsers>
<browser id="IE11" parentID="Mozilla">
<identification>
<userAgent match="Trident\/7.0; rv:(?'version'(?'major'\d+)(\.(?'minor'\d+)?)(?'letters'\w*))(?'extra'[^)]*)" />
<userAgent nonMatch="IEMobile" />
</identification>
<capture>
<userAgent match="Trident/(?'layoutVersion'\d+)" />
</capture>
<capabilities>
<capability name="browser" value="IE" />
<capability name="layoutEngine" value="Trident" />
<capability name="layoutEngineVersion" value="${layoutVersion}" />
<capability name="extra" value="${extra}" />
<capability name="isColor" value="true" />
<capability name="letters" value="${letters}" />
<capability name="majorversion" value="${major}" />
<capability name="minorversion" value="${minor}" />
<capability name="screenBitDepth" value="8" />
<capability name="type" value="IE${major}" />
<capability name="version" value="${version}" />
</capabilities>
</browser>
<!-- Mozilla/5.0 (Windows NT 6.3; Trident/7.0; rv:11,0) like Gecko -->
<browser id="IE110" parentID="IE11">
<identification>
<capability name="majorversion" match="11" />
</identification>
<capabilities>
<capability name="ecmascriptversion" value="3.0" />
<capability name="jscriptversion" value="5.6" />
<capability name="javascript" value="true" />
<capability name="javascriptversion" value="1.5" />
<capability name="msdomversion" value="${majorversion}.${minorversion}" />
<capability name="w3cdomversion" value="1.0" />
<capability name="ExchangeOmaSupported" value="true" />
<capability name="activexcontrols" value="true" />
<capability name="backgroundsounds" value="true" />
<capability name="cookies" value="true" />
<capability name="frames" value="true" />
<capability name="javaapplets" value="true" />
<capability name="supportsCallback" value="true" />
<capability name="supportsFileUpload" value="true" />
<capability name="supportsMultilineTextBoxDisplay" value="true" />
<capability name="supportsMaintainScrollPositionOnPostback" value="true" />
<capability name="supportsVCard" value="true" />
<capability name="supportsXmlHttp" value="true" />
<capability name="tables" value="true" />
<capability name="supportsAccessKeyAttribute" value="true" />
<capability name="tagwriter" value="System.Web.UI.HtmlTextWriter" />
<capability name="vbscript" value="true" />
</capabilities>
</browser>
</browsers>
Andrew Pallant (@LdnDeveloper) has been a web, database and desktop developer for over 16 years. Andrew has worked on projects that ranged from factory automation to writing business applications. Most recently he has been heavily involved in various forms for ecommerce projects. Over the years Andrew has worn many hats: Project Manager, IT Manager, Lead Developer, Supervisor of Developers and many more - See more at: http://www.unlatched.com/#sthash.8DiTkpKy.dpuf
