i draw a line with points (10,10),(100,10) first
,then draw a triangle with points as (10,10),
(100,10),(100,100).Does the triangle cover the line? i have tested this on different video cards and had different results.On intel 82865 card the line draws beside the triangle, and on sis(*) card the line is covered with the triangle.How to resolve this difference?

If you are using orthographic projection, and you want predictable rasterization, per the rules in the spec you need to draw points and lines on 0.5 px centers, and triangles/quads/polygons on 0.0 px corners.

Otherwise, the position of the point/line (after mvp projection and viewport transform) may be rounded up or down to the nearest integer pixel, it is implementation dependent which way it goes.