<div class="textbox-column label">
        <div>User Name:</div>
        <div>Password:</div>
    </div>
    <div class="textbox-column input">
        <div><div class="hack">#</div><input type="textbox" name="username" /></div>
        <div><div class="hack">#</div><input type="password" name="password" /></div>
    </div>
    <div class="clear"></div>

div.clear {
    clear:  both;
}

.textbox-column {
    line-height:1.6em;
}
.textbox-column.label {
    float:  left;
    margin-right:1em;
}
.textbox-column.input {
    float:  right;
}
.textbox-column .hack {
    display: inline;
    width: 1em;
    margin-right: -1em;
}

<div class="row">
    <label for="username">Username:</label>
    <input type="text" id="username" />
</div>

<div class="row">
    <label for="password">Password:</label>
    <input type="password" id="password" />
</div>​

.row {
    overflow: auto;
}

.row label {
    float: left;
    min-width: 100px;
}

.row input {
    float: right;
}