Originally Posted by jennefere
...Is there something wrong with my stylesheet?
Can someone help me?
Either there's something wrong with the stylesheet or with the code you've used in the ePub. Done correctly, you should be able to get very much the same formating in the MOBI as you are seeing in the ePub.
Where you went wrong is impossible to say without seeing both the code used for the ePub document page and the CSS stylesheet. There are a number of CSS attributes that do not have analogs in MOBI. Converters, like calibre, attempt to replace these with MOBI compliant tags, and such, but don't succeed with everything. Also, the Kindle default behaviors can be a bit different than those commonly seen in ePub readers. Leaving some attributes unstyled can lead to differences between the ePub and MOBI displays. The simple vertical spacing in your example is quite doable in MOBI.
BTW, calibre's ebook viewer is not the best choice for previewing/testing ePubs and it is a horrid choice for any other format. It's a good viewer, but it can't read anything but one format and converts others on-the-fly.
For testing ePubs on a desktop computer the best choice is Adobe Digital Editions
(aka ADE). While its the best you can get for the purpose, it isn't great. For MOBI formats, the tool to use is Kindle Previewer
, not Kindle for PC/Mac.