It is common in English to use mixed conditionals. These are usually a combination of the second and third conditionals. For example:

• If I was living in Paris, I would be eating fresh croissants every day. (I’m not living in Paris so I can't eat those croissants).

This example is the most common mixed conditional.

• In the condition clause: if + past perfect simple/continuous (third conditional)
  • E.g. "If I was living in Paris..."
• In the result clause: would, could, might + infinitive/continuous form (second conditional)
  • E.g. "I would eat fresh croissants every day."

Here are some examples of this type of mixed conditional:

• If they hadn’t built an apartment block opposite my house, I would be able to see the mountain. (They did build an apartment block and I’m not able to see the mountain).
• I wouldn’t have a lot of damage to my car if another driver hadn’t crashed into me. (I do have a lot of damage to my car because another driver crashed into me).
• If Terry hadn’t been reading his Facebook page when his boss walked in, he would still be working at the office. (Unfortunately, he was reading his Facebook page so he isn’t working at the office anymore).

However, it is also possible (though less common) to use this form:

• In the condition clause: if + past simple/past continuous (second conditional)
• In the result clause: would, could, might + perfect infinitive/continuous form (third conditional)

Here are some examples of this type of mixed conditional:

• If I was living in Paris, I would have gone to the Madonna concert. (I'm not living in Paris so I couldn't go to the concert.)
• I could have made a fortune by now if I understood the stock market. (I haven’t made a fortune because I don’t understand the stock market).
• We wouldn’t have been searching for their house if we had Google Maps on our phones. (We were searching for their house because we don’t have Google Maps on our phones).

I hope this has helped to clarify mixed conditional forms. To learn more about the other types of conditionals, have a look at Common conditional forms and Alternatives to 'if' in conditional sentences.