There are some rules when you can omit the article, but none that apply for your example. It is however a common (or at least not unseen) usage to omit indefinite articles in an enumeration or logical unit. Take for example the following sentence.
I live in an apartment with a big balcony.
Technically correct translated this would be:
Ich lebe in einer Wohnung mit einem großen Balkon.
Yet it doesn't make sense to expect a definite article in front of the balcony and therefore some people omit the article. Resulting in the (technically) wrong sentence:
Ich lebe in einer Wohnung mit großem Balkon.
The omit can be especially be observed when the sentences are already shortened (advertisements, short descriptions, etc).
Articles can be omitted for:
- Uncountable objects
- Plural of indefinite objects
- Abstract properties and emotions
- Form of address
- Names (both personal and geographically)
- Nouns after volume, weight or counts
- In proverbs
Of course there are some more specifics to when you can omit the article, the most notable is that you are talking about something unspecified. Furthermore there are some exceptions (e.g. countries that come with an article such as the Netherlands - die Niederlande).