I'm assuming when you say abc.html you're referring to the action in a controller within the MVC frameowrk. If you want to reference the .html directly you're not really using Html.ActionLink in that situation.
Lets say you have Index.cshtml and About.cshtml both within the HomeController.
To reference div with id of "testdiv" in a URL from index.cshtml (in your example abc.cshtml with id of abc) you would do the following
<a href="@Url.Action("About", "Home")#testdiv">Click me</a>
Which would generate a link of "Click Me" with a href value of /home/about#testdiv.
So you would need to do
<a href="@Url.Action("abc", "YourControllerName")#abc">Clcik me</a>