It's different from site to site. Sometimes it may be a cache issue on the server end where it may be refreshing, where you'd find yourself in a desktop view of the site while the mobile version is refreshing. Or, it may be that they just published/authorized a mobile version of the site. Unfortunately Safari (unless it's implemented in the mobile view at the bottom of the page) does not allow for device profiling or desktop request. Chrome does offer a desktop request. Other browsers such as Mercury allows you to change your profile selectively to say Desktop, Internet Explorer, Mozilla, Safari Desktop, etc, which will produce a desktop-only view.