lines are very widely spaced. I know it has something to do with the fact that each line contains one or more icons, but these icons are very tiny (15×20).
Is there any html tag I could use to have the lines more close to each other?
Thanks in advance,
Two reasons: a) images have default space around them, b) paragraphs have default space below them. So you need to separate each line by a line break, not a paragraph break, and you need to replace all of these: style="margin-bottom:-1px;"
with style="margin:4px 0 -1px;"
Check the result, and if you want them even tighter, replace the 4px with a smaller value.