So the first thing to check is that you are using a web project (if you have a Java project, be sure to add Web Capabilities to that project). This will setup the paths so MyEclipse understands your project.
Assuming that quick step above doesn’t help, we need to start with the [URL=http://www.myeclipseide.com/PNphpBB2+file-viewtopic-t-393.html]Posting Guidelines[/URL], please post that information for me. (There are so many innocuous little things that can stop autocomplete from working, so narrowing it down quickly requires a bit of info).