ive seen people talking about a DOF preview button on the e300 but i dont believe it. ther is nothing inthe manual about one. but if there is one it could help me so much. any help?

I just checked the E-300 specs on the Olympus Web site and depth-of-field-preview is listed. It says the feature is accessed via the "Preview Button." I checked the PDF version of the manual they have online and you use the "OK" button to acess the Preview function. See the screenshot from the manual that I've attached.