Display text on MouseOver for image in html

You can use title attribute.

<img src="smiley.gif"  title="Smiley face"/>

You can change the source of image as you want.

And as @Gray commented:

You can also use the title on other things like <a ... anchors, <p>, <div>, <input>, etc. See: this

You can use CSS hover
Link to jsfiddle here: http://jsfiddle.net/ANKwQ/5/

HTML:

<a><img src='https://encrypted-tbn2.google.com/images?q=tbn:ANd9GcQB3a3aouZcIPEF0di4r9uK4c0r9FlFnCasg_P8ISk8tZytippZRQ'></a>
<div>text</div>
​

CSS:

div {
    display: none;
    border:1px solid #000;
    height:30px;
    width:290px;
    margin-left:10px;
}

a:hover + div {
    display: block;
}​

You can do like this also:

HTML:

<a><img src='https://encrypted-tbn2.google.com/images?q=tbn:ANd9GcQB3a3aouZcIPEF0di4r9uK4c0r9FlFnCasg_P8ISk8tZytippZRQ' onmouseover="somefunction();"></a>

In javascript:

function somefunction()
{
  //Do somethisg.
}

​