I saw a mezuzah parchment where it seems that the while the letters where all in a line, in the sense that they did not collide with the rows above or below them, but within the row, the letters were not necessarily right next to each other. I.e., some letters were slightly higher or lower than the letter next to them.
Would this still make the mezuzah kosher?
I'll see if I can get a pic of it that I can upload.
This is difficult to answer without a picture. Let's see if this helps.
The scores on the parchment are called sirtut and are mandatory on a mezuza (Hilchot Mezuza 1:12). They help to write straight.
R Yerachmiel Askotzky in his book Tefillin and Mezuzos writes (p. 136-137)
If the writing is not in a straight, horizontal line, the parchment is passul and irreparable according to all poskim. Letters that are written very slightly below the sirtut are acceptable. If there is writing clearly below the sirtut, some poskim say it is still kosher as long as the writing is straight. According to other poskim, writing below the sirtut will make a parchment passul. [...] If the writing is wavy or on an angle, it is passul and irreparable.
In other words as long as letters are within the bounds of - or very slightly below/above - the sirtut then the mezuza is OK. If they are clearly below/above then you get into a machloket.
Net net it is always better to show these questionable parchments to a reputable sofer.
