I created the following calculated column in a list which concatonates the List Item's ID property into a HTML Anchor Tag. When the user clicks the link the user is taken to the page specific to the item by virtue of the TestID querystring parameter. Here is the formula I use to generate the hyperlink.
="<a target=_blank href=/sites/SomeSite/SitePages/SomePage.aspx?`TestID="&ID&">Overview Page</a>"`
When I initially define this calculated column all is well and all the links work fine for every item in the list. However, when I edit the properties of any particular list item and then save it, the concatenation fails so the query string of that item is changed omitting the actual ID number like so: "TestID="
Now when the user clicks the link there is no value in the TestID query string so the page's QueryString Filter fails to display the proper item properly.