Ok, you should note that the web site design has a lot of influence over this. CSS (style sheet) rigid control over some web sites (a developer deficiency) can prevent certain web sites from behaving as you would like when zoomed. The fix is to either completely disable style sheets (possible in Firefox) or to use a browser plugin that allows you to override certain style sheet and other formatting attributes used by the site developer. Some will allow you to pick and choose which attributes to honor and which to ignore.
There are a lot of poorly developed corporate web sites out there that demonstrate many developers clearly are unaware of W3C standards. CSS has compounded the problem.