The spider family Theridiidae gets it's common name from the structure of the webs. An apparent chaotic tangle, the web is in fact an ingenious trap consisting of vertically stretched threads that are attached to the ground with globs of gum. When the potential prey walks into one of the threads, it retracts and the prey is flung into more threads, thus immobilising it. . This family includes one of the most infamous of Australian spiders, the Redback, Latrodectus hasselti. However the spiders below belong to the closely related genus, Steatoda.
These tend to be smaller that the Redback but you will notice some similarity in form. Some even exhibit a small red spot. These are extremely common in my backyard and can be found under just about any rock (and believe me, as a vegetable gardener, when I tell you I have a lot of rocks here). I have even found them a good 600mm below the surface in a small cavity under a rock.
It is said a bite can induce headache and nausea but bites are not common due to the small size of the fangs.
(Click on Photos to Enlarge)