URL Mapping in asp.net

Hi,
I am using url mapping for set of urls to redirect to another page
<add url="~/Sample - EXAMPLE.htm" mappedUrl="~/default.aspx?ID=1&amp;yID=111" /> This is example of my url mapping . when I give "www.myweb.com/sample - Example.htm" it is not redirecting to the default.aspx page. but when i give "www.myweb.com/sample - EXAMPLE.htm" it is redirecting to the default.aspx page.
Why it is not redirtecting if it is in lower case letters?? Is it case sensitive??

Please help me