Width and height properties for the legend that will provide firm dimensions in pixels, so regardless of the series names' length, it will always have constant size.
You can set width and height through the kendo widget:
		<script>
			function pageLoad() {
				var chart = $find("<%=DonutChart.ClientID%>").get_kendoWidget();
				chart.options.legend.height = 80;
				chart.redraw();
			}
		</script>
		<telerik:RadHtmlChart runat="server" ID="DonutChart" Width="500" Height="500" Transitions="true">
			<Appearance>
				<FillStyle BackgroundColor="White"></FillStyle>
			</Appearance>
			<ChartTitle Text="OS Usage Statistics for December 2012">
				<Appearance Align="Center" Position="Top"></Appearance>
			</ChartTitle>
			<PlotArea>
				<Series>
					<telerik:DonutSeries>
						<LabelsAppearance Visible="false">
						</LabelsAppearance>
						<TooltipsAppearance DataFormatString="{0}%" BackgroundColor="White"></TooltipsAppearance>
						<SeriesItems>
							<telerik:PieSeriesItem BackgroundColor="#00adcc" Name="Win7"
								Y="55.6"></telerik:PieSeriesItem>
							<telerik:PieSeriesItem BackgroundColor="#cccccc" Name="Win8" Y="2.5"></telerik:PieSeriesItem>
							<telerik:PieSeriesItem BackgroundColor="#999999" Name="Vista" Y="2.8"></telerik:PieSeriesItem>
							<telerik:PieSeriesItem BackgroundColor="#888888" Name="NT" Y="1.8"></telerik:PieSeriesItem>
							<telerik:PieSeriesItem BackgroundColor="#777777" Name="WinXP" Y="21.1"></telerik:PieSeriesItem>
							<telerik:PieSeriesItem BackgroundColor="#666666" Name="Linux" Y="4.7"></telerik:PieSeriesItem>
							<telerik:PieSeriesItem BackgroundColor="#555555" Name="Mac" Y="8.7"></telerik:PieSeriesItem>
							<telerik:PieSeriesItem BackgroundColor="#444444" Name="Mobile" Y="2.2"></telerik:PieSeriesItem>
						</SeriesItems>
					</telerik:DonutSeries>
				</Series>
			</PlotArea>
		</telerik:RadHtmlChart>

Axes themselves do not have tooltips, only series do. Thus, tooltips cannot be added to the y-axis.
Add

Set tooltips of points between series points  - http://screencast.com/t/Q7FYJxkouLA

The functionality is similar to the one in Kendo UI Chart (http://demos.telerik.com/kendo-ui/dataviz/line-charts/notes.html) :
http://dojo.telerik.com/OZuNU

For the time being you can try to utilize the kendo.drawing API in order to place the text on a particular position.  This forum may be helpful on the matter - http://www.telerik.com/forums/custom-drawing#sOkmYWbfrUW404Rr13eLDQ

Tooltips of points between series points
See: http://screencast.com/t/Q7FYJxkouLA

1.Today: When vertical axis are out of navigator range from to
they are seen.
2.Suggtion: Give option to programmer to choose if to show or hide.
3.The same idea for plot bands,

We are trying to convert a websites 11 year old controls from a different vendor to telerik.  All of the controls have been replaced except for the RadHtmlChart, which has limited customization of the legend.  Specifically we have the following issues:

1) The legend color squares are too small.  You can see the difference in the attachment "competitor" vs "telerik".  REQUEST: Set the size of the color squares.
2) The legend spacing between items is not customizable and is too compressed for our liking.  See "competitor" vs "telerik" to see the difference.  REQUEST: Allow padding or margin between legend items.
3) The legend size cannot be set to a fixed width.  For a left aligned legend, this results in multiple charts having inconsistent alignment.  Setting a different margin for each chart individually does not fix the problem.  Depending on the data fed to the charts, their position changes.  See the "multiple-charts" attachment for an example. REQUEST: Allow a fixed legend size so multiple charts can be aligned.
4) For left-aligned charts, the legend cannot be set to the top.  REQUEST: Allow TopLeft, TopRight options for legend alignment.

Thank you,
David A.

A functionality similar to KendoUI's error bars - http://demos.telerik.com/kendo-ui/dataviz/line-charts/error-bars.html

If set to true the chart will round the first and last date to the nearest base unit.

There are two workarounds you can use in the meantime

- Use string representations of the dates instead of actual dates. In this manner you can bind the chart to strings and use a "regular" categorical axis and then the plot bands will work based on the index of the item. In such a case you will need to aggregate the data yourself before passing it to the chart.
- Using the Kendo Chart widget directly, and here is an example of using date objects and adding plot bands dynamically: https://docs.telerik.com/kendo-ui/controls/charts/how-to/appearance/dynamic-plot-bands

Here is also a basic example of fetching the Kendo Chart scripts through a hidden RadHtmlChart so that you can easily use the Kendo Chart widget

<script>
    var myData = [{
        "day": new Date("2014/01/01")
    }, {
        "day": new Date("2014/01/02")
    }, {
        "day": new Date("2014/01/31")
    }];
 
 
    function addPlotBand() {
        $ = $telerik.$;
 
        var start = new Date(2014, 0, 1 + Math.floor(Math.random() * 30));
        var end = new Date(start.getTime() + 1000 * 3600 * 24); // 24 hours after start
 
        var options = {};
 
        options["categoryAxis"] = {
            plotBands: [{
                from: start,
                to: end,
                color: "green"
            }]
        };
 
        $("#chart2").data("kendoChart").setOptions(options);
    }
 
    function pageLoad() {
        $ = $telerik.$;
        $("#chart2").kendoChart({
            dataSource: {
                data: myData
            },
            categoryAxis: {
                type: "date",
                field: "day"
            }
        });
    }
</script>
<telerik:RadButton ID="RadButton1" runat="server" AutoPostBack="false" OnClientClicked="addPlotBand" Text="add plotband" />
<div id="chart2"></div>
<telerik:RadHtmlChart runat="server" ID="chart" Style="visibility: hidden;">
    <PlotArea>
        <XAxis DataLabelsField="day">
        </XAxis>
    </PlotArea>
</telerik:RadHtmlChart>

For the time being the DateTime object can be set to the AxisCrossingPoint on the client. For example:

ASPX:

		<script>
			function OnLoadHandler(sender, args) {
				var kendoChart = sender.get_kendoWidget();
				var opts = kendoChart.options;
				opts.categoryAxis.axisCrossingValues = [0, new Date("2014, 11, 05, 19:15:00")];
				kendoChart.setOptions(opts);
			}
		</script>
		<telerik:RadHtmlChart runat="server" ID="RadHtmlChart1" Width="600px" Height="400px">
			<ClientEvents OnLoad="OnLoadHandler" />
			<PlotArea>
				<Series>
					<telerik:LineSeries Name="Product 1" DataFieldY="SellQuantity">
					</telerik:LineSeries>
				</Series>
				<XAxis DataLabelsField="SellDate" BaseUnit="Minutes">
					<LabelsAppearance Step="15"></LabelsAppearance>
					<MinorGridLines Visible="false" />
					<AxisCrossingPoints>
						<telerik:AxisCrossingPoint Value="10" />
					</AxisCrossingPoints>
				</XAxis>
				<AdditionalYAxes>
					<telerik:AxisY></telerik:AxisY>
				</AdditionalYAxes>
			</PlotArea>
			<ChartTitle Text="LineSeries"></ChartTitle>
		</telerik:RadHtmlChart>


C#:
	protected void Page_Load(object sender, EventArgs e)
	{
		if (!Page.IsPostBack)
		{
			RadHtmlChart1.DataSource = GetData();
			RadHtmlChart1.DataBind();
		}
	}

	protected DataTable GetData()
	{
		DataTable dt = new DataTable();

		dt.Columns.Add("ID", typeof(int));
		dt.Columns.Add("SellQuantity", typeof(int));
		dt.Columns.Add("SellDate", typeof(DateTime));

		dt.Rows.Add(1, 2, new DateTime(2014, 11, 05, 18, 22, 22));
		dt.Rows.Add(2, 5, new DateTime(2014, 11, 05, 18, 56, 22));
		dt.Rows.Add(3, 6, new DateTime(2014, 11, 05, 19, 14, 22));
		dt.Rows.Add(4, 4, new DateTime(2014, 11, 05, 19, 48, 22));
		dt.Rows.Add(5, 7, new DateTime(2014, 11, 05, 20, 12, 22));

		return dt;
	}

Declined with the following reason - chart series are preserved in the ViewState by default. You can do one of the following:
1) Either disable the ViewState of the chart or its container:
ASPX:
<asp:Panel ID="Panel1" runat="server" EnableViewState="false" />
C#:
		RadHtmlChart chart1 = new RadHtmlChart();
		chart1.EnableViewState = false;
2) Or clear the chart Series collection after adding the chart to the page:
		RadHtmlChart chart1 = new RadHtmlChart();
		chart1.ID = "myChart";
		//Add the chart to the page
		Panel1.Controls.Add(chart1);
		//Clear the series after adding the chart to the page
		chart1.PlotArea.Series.Clear();

inkspace not suitable for radhtmlchart exporting.   Because inkspace does not work in windows server 2008 R2. So please provide direct exporting feature for radhtmlcharts.

Please provide RadHtmlChart Export features

When viewing a line chart with multiple series, the RadHtmlChart automatically changes shapes for each series to make it easy to distinguish, however the shapes are not carried over to the legend.  This means a user printing on a black & white printer will have no way to distinguish the different series (since the shapes are not in the legend).

For the time being the property (http://docs.telerik.com/kendo-ui/api/javascript/dataviz/ui/chart#configuration-legend.border) can be set through the chartObject. For example:
JavaScript:
	<telerik:RadCodeBlock ID="RadCodeBlock1" runat="server">
		<script>
			function pageLoad() {
				var chart = $find("<%=PieChart1.ClientID%>");
				chart._chartObject.options.legend.border = { width: 2, color: "green", dashType: "longDashDotDot" }
				chart.repaint();
			}
		</script>
	</telerik:RadCodeBlock>
ASPX:
		<telerik:RadHtmlChart runat="server" ID="PieChart1" Transitions="true">
			<PlotArea>
				<Series>
					<telerik:PieSeries StartAngle="90">
						<LabelsAppearance Position="OutsideEnd" DataFormatString="{0} %" />
						<TooltipsAppearance DataFormatString="{0} %" />
						<SeriesItems>
							<telerik:PieSeriesItem BackgroundColor="Purple" Exploded="true" Name="Internet Explorer" Y="18.3" />
							<telerik:PieSeriesItem BackgroundColor="Orange" Exploded="false" Name="Firefox" Y="35.8" />
							<telerik:PieSeriesItem BackgroundColor="Green" Exploded="false" Name="Chrome" Y="38.3" />
							<telerik:PieSeriesItem BackgroundColor="Blue" Exploded="false" Name="Safari" Y="4.5" />
							<telerik:PieSeriesItem BackgroundColor="Red" Exploded="false" Name="Opera" Y="2.3" />
						</SeriesItems>
					</telerik:PieSeries>
				</Series>
			</PlotArea>
			<ChartTitle Text="Browser Usage for April 2012">
			</ChartTitle>
		</telerik:RadHtmlChart>

So cool RadHtmlChart navigator should be able to be attached to non-stock layout charts, support multiple databound series and y-axis items other than financial data