Application opens in different IE browser mode and document

Hi All,

I have an asp.net web application hosted in IIS. I am using IE 9 browser. I have a bit of confusion regarding IE browser mode and document mode. Because if I am using 'localhost' word in the login URL(i.e. http://localhost/MyWebApplication/Login/Default.aspx) of application then it opens with 'IE 9' browser mode and 'IE 9 standard' document mode, which is fine.

But when I open the same application with same client browser version having my IP in the URL(i.e. http://255.255.255.255/MyWebApplication/Login/Default.aspx) then it opens with 'IE 9 Compatibility view' browser mode and 'IE 7 standard' document mode.

So, now I am not sure how IE internally decides browser mode and document mode based on the URL. What is the difference in having IP or 'localhost' in the URL?

Also, I tried adding meta tag in my pages to force the IE to work with specific document mode, it works fine. But, by default there no meta tag or any other configuration which helps IE to decide document mode or browser mode.

Can anyone help me in this?..