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How can I eliminate the extra space added to the bottom when the value dips below 0 on the Y axis in Chart.js?

I styled my chart with a legend below it like this, and you'll see a grey chart faintly rendered on another chart behind it for comparison (their data scales are different, couldnt put them both on the same actual chart):
As you can see, because the data on the front chart dipped below zero on the Y axis, 0 on the Y axis was moved upward way further than it needed to (the bottom of the chart normally lines up with the bottom of the gray chart behind it). I can of course resize and move the gray chart so that it's Y0 and the front chart's Y0 align, but that still leaves a big gap between the lowest data on the chart and the legend.
How can I eliminate this extra space below the lowest data rendered on the chart? I want the lowest value rendered to touch the bottom on the chart.
Putting my code, I think, wouldn't be useful here, since this behavior seems to be universal across Chart.js, and what I'm looking for is probably a setting in the options object that I don't know of yet, or know of, but don't know it can produce the desired result.

Found the setting for it:
yAxes: [{
ticks: {
autoSkip: true,
maxTicksLimit: 0,
stepSize: 0.1
}
}]

Alter first vertical grid line in nvd3

I want to remove (or make effectively hidden) the first vertical line in the grid for an nvd3 chart. I thought it was a problem with my chart, but after testing it, I realized it seems to be a more general problem.
I tested it by running the line:
d3.selectAll('.tick, .nv-axislabel, .nv-axis text').attr('fill','#999999')
in the console, at the simplest line chart I could find: http://nvd3.org/examples/line.html and it still didn't work! It changes all the lines except the very first vertical line. I'm baffled, I've tried every combination of classes with stroke, fill, opacity, etc - I can either affect the entire svg (with opacity), or nothing. Anyone have any ideas?
EDIT:
I should have specified this originally, I apologize - I do not want to remove the Y axis entirely. I still need the label and the tick marks - I just want to remove that one vertical line (or at least lighten it - it is much darker than the rest of my chart).

Going by your comments:
You don't want to see the " the first vertical line in the grid for an nvd3 chart"
Which is the y axis:
Two ways to achieve that:
Option1
var chart = nv.models.lineChart()
.margin({left: 100}) //Adjust chart margins to give the x-axis some breathing room.
.useInteractiveGuideline(true) //We want nice looking tooltips and a guideline!
.transitionDuration(350) //how fast do you want the lines to transition?
.showLegend(true) //Show the legend, allowing users to turn on/off line series.
.showYAxis(false) //hide the y-axis
.showXAxis(true); //Show the x-axis
Option2:
Since in your example you are going for a CSS option
d3.selectAll('.nv-y').attr('display','none')
I will prefer Option1
EDIT post your clarification, you wish to make the y axis line light you can use:
d3.selectAll('.nv-y path').attr('opacity','0.1')
or if you want to hide it completely
d3.selectAll('.nv-y path').attr('display','none')

One solution is to specify an array of tick values that you want to use for each axis. Use axis.tickValues([values]) to explicitly declare which XAxis ticks you want for your graph. So you could pop .tickValues([1, 2, 3, 5, 8, 13, 21]); into either the chart.xAxis or the chart.yAxis, and ticks would only appear from the corresponding values in the array. In your case, you would want to put it in the chart.xAxis variable. However if you want to have a dynamic chart, explicitly declaring the tick values would pose a problem once the data is updated in the graph. If on the other hand you are using static data, this is a pretty easy fix. I've tested this solution in their live code editor and it seems to do the trick.
Refer to https://github.com/mbostock/d3/wiki/SVG-Axes#ticks to see some other directives that could be of use.

highstocks hozontal line won't draw

So I'm trying to get my highcharts plot to draw the recent minima and maxima.
I already figured the correct JSON sub-object is "plotLines", however my script just refuses to draw them without any error. Maybe someone of you can spot my error. The corresponding (and probably wrong, but that doesn't really matter for this example) values are listed to the left
thanks!

With you current values, the lines will never plot.
Your axis min is sitting at 500, and you are plotting lines at 498.
The axis will not expand to show plotLines or plotBands - it will only expand to show data (or based on minPadding/maxPAdding, etc).
You will need to check that your lines are within your axis min/max in order to display them.
You can do that by using the getExtremes() method, and if needed, the setExtremes() method:
http://api.highcharts.com/highcharts#Axis.getExtremes
http://api.highcharts.com/highcharts#Axis.setExtremes
Edit to incorporate comments:
If the line is the same value as a grid line, you will need to set a zIndex on either the plotLine or the gridLines - by default the gridLines are above the plotLines

Highcharts - Series tooltip doesn't work when plotting lines that zigzag on the x axis

I have a highcharts chart that I need to plot but which has lines which can go back on themselves on the X Axis.
e.g. jsfiddle example
My problem isn't that I can't plot it but rather the series tooltips don't display correctly.
If you zoom right in to individual points they seem ok, but not at normal zoom level.
E.g. if you scan your mouse across the series from right to left it doesn't want to show you the tooltip on x Value 1, intead it jumps to the second set of values on x value 2.
I've changed the tooltips to being not shared:
tooltip: {
shared: false,
},
but this has made little difference, apart from now it seems to work when zoomed in, but I suspect this is only because there are only one set of x Axis values visible.
Does anybody know how it is possible to configure Highcharts to allow for series where the x values aren't sorted either ascending or descending as I can't find anything in the documentation.

From the API documentation:
Note that line series and derived types like spline and area, require
data to be sorted by X because it interpolates mouse coordinates for
the tooltip. Column and scatter series, where each point has its own
mouse event, does not require sorting.
So change your series to type: 'scatter' with a lineWidth > 0. Here's an updated fiddle.

Decimal values for yAxis categories in Highcharts

I need my yAxis categories to be 0 = 'Poor', 0.25 = 'Below Average', 0.75 = 'Average' 1="Good"
I set the categories right, but Highcharts seems to interpret each point I plot to be equal to "1" step on the yAxis. See http://jsfiddle.net/54cFG/
Ideally, that chart should always show 4 labels on the yAxis and the plotted points should line up at "Below Average" and "Average".
Is there a setting I'm missing? I think I pretty much tried everything at http://www.highcharts.com/ref/

You could always use plot bands to display categories on the Y axis. That way you could still keep the actual values. I have demonstrated that with your code here.
EDIT
Here is another example with the grid lines taken off and the plotBands each with their own color. Here is the color chart if you wan to change any of them.
If you prefer to use the plot bands and no y-axis labels, here is an example of that. I think it works just fine. If the user really wants to see the exact value they can hover over the point.