ASP.NET repeater control overlapping for some users

My whole websites makes use of the ASP.NET(2.0) repeater control and I have been getting some complains from people that they cant view my site as the controls are overlapping.

This sounds like a browser issue to me as I never see it in IE8 or IE7 or Chrome or Firefox.

Any idea why this is happening? What should I do to prevent this from happening?

Sounds like a Microsoft issue?

As far as the browser is concerned, there's no such thing as an ASP.NET repeater control (indeed, to the browser, there's no such thing as ASP.NET); the browser cares only about the resultant HTML and CSS.

The first thing I would do is to make sure the HTML is valid, while browsers will do incorrect things with valid HTML, testing its validity is a quick way to catch a lot of errors that can cause problems (in particular, where the tags aren't correctly nested). I use this firefox plugin that is imperfect but quick to use.

This isn't guaranteed to be your issue, but it's definitely the place to start.

The only way you are going to find out what is happening is to check your site in various browsers. You should at least be testing in Firefox, Chrome and IE (arguably 6 and above).
The issue is most likely css markup not being cross browser compliant.
A lot of developers go with process of get it working in Firefox, and then fix any quirks in IE. The Firefix Firebug plugin is ideally suited for testing and modifying css. IETester is also handy for testing various versions of IE in one application.