I use Dreamweaver to design my webpages, and throughout the last few years I have had some people complain that all the text is jumbled on the pages. This is always fixed by them just changing the text size back to medium in their browser. But I am wondering if it is my page that is somehow changing their browser's selected text size to large, or is that something that doesn't have anything to do with me. And if it is not my website's fault, why would the other sites be showing up fine on their computers, but mine does not. Any help is greatly appreciated. Thanks.
Are you using standard fonts? You should use % with fonts really anyway, I don't always do it myself but it's good practice.
Setting % is the best way to go, it will make your font size relative to your other site's objects (tables: make sure those are set at % too). The font size will be more fixed rather than varying from resolution to resolution.
You could also try sizing your fonts with "em" instead of px or pt. That way the font displayed is relative to what the browser's font size is set to.