So if you're having odd issues with a JavaScript function like WebForm_InitCallback(); which is a built in ASP.NET JavaScript function and you are using the
HTTP Compression Handler from blowery and you are testing a site on the ASP.NET development server, I may have a fix for you.
In your web.config you should add an exclude statement to exclude the WebResource.axd path:
<httpCompress preferredAlgorithm="gzip" compressionLevel="high">
<excludedMimeTypes>
<add type="image/jpeg" />
<add type="image/gif" />
<add type="image/png" />
</excludedMimeTypes>
<excludedPaths>
<add path="WebResource.axd"/> </excludedPaths>
</httpCompress>