As Jeff points out over in this question, this has been discussed to death over on the Marvel Wiki.. But, to save you wading through pages of debate:
Take a look at the Web-Shooters page on the aforementioned Wiki; it basically says what he has said a few times in the comics; they have settings that allow him to adjust what he shoots.
The effect of the very small turbine pump vanes is to compress (shear) the web fluid and then force it, under pressure, through the spinneret holes which cold-draws it (stretches it: the process wherein nylon gains a four-fold increase in tensile strength), then extrudes it through the air where it solidifies. As the web fluid exits the spinneret holes, it is attracted to itself electrostatically and thus can form complex shapes. The spinneret holes have three sets of adjustable, staggered openings around the turbine which permit a single web line, a more complex, spun web line, and a thick stream.
(Emphasis added to specifically address your question.)
To link them up to your specific question details:
- Globs of sticky webbing --> a thick stream.
- Lines of swinging webbing --> spun web line
- Sticky lines of webbing. --> single web line