There is a new attribute of the <input> tag in HTML 4 which is not uniformly supported by the browsers which will prevent the editing of a text field:
<input type="text" name="text1" readonly>
This input field can receive the focus but cannot be changed by the user.
Keep in mind that this will not work with all browsers. The "disabled" attribute of an input field will prevent its contents from being edited, but it will also prevent the contents from being submitted with the form. This works with more browsers than "readonly", but the behavior is still spotty from browser to browser. Remember to test thoroughly with all browsers.