how to set a global variable that is referenced throughout the site? i'm trying to avoid programming and hoping i could do this with modules:

I have a classified ad's website which has about 100 categories where users can add an advert. The thing is these are all linked to a location. So i use two vocabularies- one of categories and one of locations.

I want to be able to allow the user to select a location when they first land on the site from a dropdown and then when the user moves through the site this is referenced. I have two specific use cases


When the user goes to add a listing, their location is pre-selected in reference to the one they already selected at the initial visit.
When the user returns they only see adverts relating to their town/city (consider them being already registered)
Ok. With next to no programming I would recommend trying to use the Session Cache API. This module allows for simple items to be stored in say a cookie, even for Anonymous users. You may want to try to use it directly, or use a module that already makes use of it, such as:

Views Global Filter, this module allows you to set an exposed views global filter your visitors fill out once -- and it's remembered for the duration of their visit. As they visit throughout your website your other views pages or blocks would query the existing saved off global filter values in cache and be shown the listings you want.