Check and see if it has 75-300 written on it. If so, its horrible. That lens is not very good. It was a cheap lens meant for use on lower resolving film bodies. See if you can dump it and pick up a 55-250. A much better lens but still quite affordable.
or a 70 210 3.5 canon if you are into sports about 100$
a 70 300 for about 300$, wait for a sale on canon refurbished site
for a general inexpensive lens, the 55-250 rocks