Does liquid temperature matter when making bread in a bread maker?

With a bread maker, it's important to follow the recipe closely, at least until you've got a reliable result , when you can start experimenting.

Mine, for example, expects "tepid" water for most programs, which the book defines as 20-25°C. The super rapid program requires 46-51°C. Cooler and there won't be time for the yeast to get going, much hotter and the yeast will be killed before it starts to work. This also means the super-rapid program can't be used with a delayed start, as the water would cool.

As a very general rule, slower programs will be more forgiving on temperature if you don't have a suitable thermometer and don't trust your estimation.

You can get a very good idea of the temperature of the water if you mix boiling with room temperature, in known proportions, taking a weighted average. For example that super rapid program could use 2 parts room temperature to one part boiling, mixed before it reaches the yeast. If room temp is 20°C and you mix it with actually boiling water, the resulting temperature will be (2×20+1×100)/3 = 140/3 = 47°C. Ths is at the bottom of the acceptable range for my super rapid program, so I use a little over 1/3 boiling (handily it wants 260ml, so 90ml boiling made up with cold is good).

Temperature matters a lot, even with a breadmaker. Breadmaking is all about gluten development and feeding the yeast so they produce alcohol and carbon dioxide.

The water temperature will have a direct impact on how quickly the fungi propagate. In traditional breadmaking, ambient room temperature and oven temperature are also important.

Knowing what kind of bread you are making would be helpful in providing more specific advice. It's a wonderful thing to do and there are some great, really easy recipes that make delicious bread. Hopefully you'll next venture out to more traditional breadmaking which can be very easy with no-knead recipes and french oven recipes (such as Ken Forkish's).

Beside the effect on yeast growth speed mentioned in other answers, the temperature of the water also has a direct effect on gluten formation. Using the same ratio of water to flour, you will get much stiffer gluten with colder water. Of course, you cannot make use of this effect in a bread maker, since you cannot influence the other variables (especially the rising time) to compensate for a changed water temperature. So do as Chris H suggested and use the water temperature that is prescribed in your user manual - both too hot and too cold will give you unexpected (and probably undesirable) results.