HTML – Interview Questions & Answers Set – 2

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htmlHow can I check for errors?

HTML validators check HTML documents against a formal definition of HTML syntax and then output a list of errors. Validation is important to give the best chance of correctness on unknown browsers (both existing browsers that you haven’t seen and future browsers that haven’t been written yet).

HTML checkers (linters) are also useful. These programs check documents for specific problems, including some caused by invalid markup and others caused by common browser bugs. Checkers may pass some invalid documents, and they may fail some valid ones.
All validators are functionally equivalent; while their reporting styles may vary, they will find the same errors given identical input. Different checkers are programmed to look for different problems, so their reports will vary significantly from each other. Also, some programs that are called validators (e.g. the “CSE HTML Validator”) are really linters/checkers. They are still useful, but they should not be confused with real HTML validators.

When checking a site for errors for the first time, it is often useful to identify common problems that occur repeatedly in your markup. Fix these problems everywhere they occur (with an automated process if possible), and then go back to identify and fix the remaining problems.

Link checkers follow all the links on a site and report which ones are no longer functioning. CSS checkers report problems with CSS style sheets.

Do I have to memorize a bunch of tags?

No. Most programs that help you write HTML code already know most tags, and create them when you press a button. But you should understand what a tag is, and how it works. That way you can correct errors in your page more easily.

How do I set the focus to the first form field?

You cannot do this with HTML. However, you can include a script after the form that sets the focus to the appropriate field, like this:

<form id=”myform” name=”myform” action=…>
<input type=”text” id=”myinput” name=”myinput” …>
</form>

<script type=”text/javascript”>
document.myform.myinput.focus();
</script>

A similar approach uses <body onload=…> to set the focus, but some browsers seem to process the ONLOAD event before the entire document (i.e., the part with the form) has been loaded.

How can I eliminate the extra space after a </form> tag?

HTML has no mechanism to control this. However, with CSS, you can set the margin-bottom of the form to 0. For example:
<form style=”margin-bottom:0;” action=…>

You can also use a CSS style sheet to affect all the forms on a page:
form { margin-bottom: 0 ; }

How can I use tables to structure forms?

Small forms are sometimes placed within a TD element within a table. This can be a useful for positioning a form relative to other content, but it doesn’t help position the form-related elements relative to each other.

To position form-related elements relative to each other, the entire table must be within the form. You cannot start a form in one TH or TD element and end in another. You cannot place the form within the table without placing it inside a TH or TD element. You can put the table inside the form, and then use the table to position the INPUT, TEXTAREA, SELECT, and other form-related elements, as shown in the following example.

<form action=”[URL]”>
<table border=”0″>
<tr>
<th scope=”row”>
<label for=”account”>Account:</label>
</th>
<td>
<input type=”text” name=”account” id=”account”>
</td>
</tr>
<tr>
<th scope=”row”>
<label for=”password”>Password:
</th>
<td>
<input type=”password” name=”password” id=”password”>
</td>
</tr>
<tr>
<td> </td>
<td><input type=”submit” name=”Log On”></td>
</tr>
</table>
</form>

Can I have two or more actions in the same form?

No. A form must have exactly one action. However, the server-side (e.g., CGI) program that processes your form submissions can perform any number of tasks (e.g., updating a database, sending email, logging a transaction) in response to a single form submission.

How can I use forms for pull-down navigation menus?

There is no way to do this in HTML only; something else must process the form. JavaScript processing will work only for readers with JavaScript-enabled browsers. CGI and other server-side processing is reliable for human readers, but search engines have problems following any form-based navigation.

Can I use percentage values for <TD WIDTH=…>?

The HTML 3.2 and HTML 4.0 specifications allow only integer values (representing a number of pixels) for the WIDTH attribute of the TD element. However, the HTML 4.0 DTD allows percentage (and other non-integer) values, so an HTML validator will not complain about <TD WIDTH=”xx%”>.

It should be noted that Netscape and Microsoft’s browsers interpret percentage values for <TD WIDTH=…> differently. However, their interpretations (and those of other table-aware browsers) happen to match when combined with <TABLE WIDTH=”100%”>. In such situations, percentage values can be used relatively safely, even though they are prohibited by the public specifications.

Why doesn’t <TABLE WIDTH=”100%”> use the full browser width?

Graphical browsers leave a narrow margin between the edge of the display area and the content.
Also note that Navigator always leaves room for a scrollbar on the right, but draws the scrollbar only when the document is long enough to require scrolling. If the document does not require scrolling, then this leaves a right “margin” that cannot be removed.

Why is there extra space before or after my table?

This is often caused by invalid HTML syntax. Specifically, it is often caused by loose content within the table (i.e., content that is not inside a TD or TH element). There is no standard way to handle loose content within a table. Some browsers display all loose content before or after the table. When the loose content contains only multiple line breaks or empty paragraphs, then these browsers will display all this empty space before or after the table itself.

The solution is to fix the HTML syntax errors. All content within a table must be within a TD or TH element.

How can I show HTML examples without them being interpreted as part of my document?

Within the HTML example, first replace the “&” character with “&amp;” everywhere it occurs. Then replace the “&lt;” character with “<” and the “&gt;” character with “>” in the same way.

Note that it may be appropriate to use the CODE and/or PRE elements when displaying HTML examples.

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