graphics - ListLinePlot of multiple series with data value and legend appearing as the cursor moves over ploted lines

I have multiple series and I am plotting using Mma's ListLinePlot function. But I am trying to implement a feature to my plot so that I can view legend and corresponding values of the series at a particular point of the plotted lines as I move my cursor over the lines.

Here is an example: Web Browser Market Share Trends

We can use the following example codes form Wolfram Documentation to be consistent.

ListLinePlot[Table[Accumulate[RandomReal[{-1, 1}, 500]], {3}], 
 Filling -> Axis, PlotLegends -> {"First", "Second", "Third"}]

To make it more clearer, I have uploaded the following two screen prints form http://www.w3counter.com/trends.

Thank you all for making this site so useful to solve practical problems.

Answer

Using code from the mentioned 9447, with some patches

data = Transpose@{{"First", "Second", "Third"}, Table[Accumulate[RandomReal[{-1, 1}, 500]], {3}]};

hover[data_] := 
 Module[{mouse}, 
  mouse = MousePosition[{"Graphics", Graphics}, {99999, 99999}];
  {Text[Style[Framed@Column[
       (Row[{#[[1]], ": ", #[[2, Min[Length@#[[2]], Max[1, Round[mouse[[1]]]]]]]}]) & /@ data],
     Background -> LightYellow, FontSize -> 16],
    mouse, {-1.1, 2}],


   PointSize[Large],
   Point[{Min[Length@#[[2]], 
        Max[1, Round[mouse[[1]]]]], #[[2, 
         Min[Length@#[[2]], Max[1, Round[mouse[[1]]]]]]]}] & /@ data
   }
  ]

ListLinePlot[#[[All, 2]], Epilog -> Dynamic@hover[#], PlotLegends -> #[[All, 1]]]& @ data

There is some styling to do, but this could be useful as a starting point! I tried to be as verbose as possible... ugly but easier to poke around!

Lazy saturday update

A slightly prettier version that hop's on the Plot's styles and legends. Also better mirrors your example. And uses Clip!

addHover[plot_Legended] :=
 DynamicModule[{mouse, legend, data, newPlot},
  legend = 
   plot /. Legended[a_, Placed[b_, __]] :> List @@ b /. 

      HoldPattern[h : Except[LegendMarkers] -> _] :> Sequence[] /. 
     HoldPattern[Rule[_, b_]] -> List@b // Flatten[#, {{2}, {1}}] &;
  data = Cases[First@plot, Line[x__] -> x, Infinity];
  newPlot = plot;
  newPlot[[1, 2]] = Append[plot[[1, 2]], Epilog ->
     {Text[Style[Framed[Grid[{
           {Dynamic@Clip[Round@MousePosition["Graphics", {99999, 99999}][[1]], {1,Infinity}]},
           Sequence @@ MapThread[
             {Row@{Style[Dynamic@#2[[2]], #2[[1]]], ": ",                     
                 Text[Dynamic@#1[[Clip[Round@MousePosition["Graphics", {99999, 99999}][[1]], {1,Length@#1}]]][[2]]]}} &

             , {data, legend}]},
          Alignment -> Left,
          Spacings -> 0],
         FrameStyle -> LightBlue, RoundingRadius -> 10],
        Background -> Opacity[0.8, White], FontSize -> 12], 
       Dynamic@MousePosition["Graphics", {99999, 99999}], {-1.5, 0}],

      MapThread[
       {#2[[1]] /. a_ /; ColorQ@a :> Darker@a,
         PointSize[0.012],

         Point[Dynamic@#1[[Clip[Round@MousePosition["Graphics", {99999, 99999}][[1]], {1, Length@#1}]]]]} &,
       {data, legend}]
      }];
  newPlot
  ]

Now data remains unaltered!

data2 = Table[Accumulate[RandomReal[{-1, 1}, 500]], {3}]
ListLinePlot[data2, PlotLegends -> {"First", "Second", "Third"} , PlotStyle -> {Orange, Dashed, Thick}] // addHover

It will probably break if you try it with fancier plots, use DataRange or stare long enough.

There is still some important aspects missing, such as mirroring PlotMarkers, but I couldn't manage to avoid distortion when Showing or Epiloging anything that is not a Point.